I plan on playing a revised Way of the Four Elements monk (fixes most of the classes issues) for the Descent into Avernus campaign. To challenge myself, I am limiting myself to only water/ice disciplines. Before we started I used some of my gold to buy waterskins (11 total on me) and I’ll be taking Mage Initiate (Druid) for Create Water and Frostbite.
What are some creative or useful ideas you can think of for Shape Water and Shape the Flowing River?
Edit: If I were to create a wall of ice using the 5 gallons of water I have access to, should I use the Wall of Ice spell stats (8 AC / 10 hp per 5 ft of wall)?
Kind of thought about that, however, won’t that create difficult terrain? Can I even climb on those without them breaking?
Depending on its crystal structure, ice can have a shear strength over 50 PSI. So a 2 inch diameter ladder rung could support 300lb. And that strength increases exponentially, increasing diameter from 2in to 3in more than doubles it.
Slipperiness could be a concern, but the description of these techniques don't imply that the ice melts, so a rough texture on the top should provide necessary traction.
Edit: If I were to create a wall of ice using the 5 gallons of water I have access to, should I use the Wall of Ice spell stats (8 AC / 10 hp per 5 ft of wall)?
The intent of Shape the Flowing River class feature for Monks of the Way of the Four Elements, seems to be simple forms:
Raise/lower ice elevation, cut/fill a trench, raise/lower a wall, or form a pillar. Note the wording on each example reads "a trench", "a wall", "a pillar", not multiples.
(It also says "The extent of any such changes can’t exceed half the area’s largest dimension. For example, if you affect a 30-foot square, you can create a pillar up to 15 feet high, raise or lower the square’s elevation by up to 15 feet, dig a trench up to 15 feet deep, and so on. You can’t shape the ice to trap or damage a creature in the area.")
I think the intent is to create one basic formation per usage of the feature. I'm not even certain stairs would qualify, though it seems reasonable in context.
That last bit about how it can't be shaped "to trap or damage a creature" worries me too:
Does that mean a bowl or funnel shape is out of the question because it could trap creatures?
What if there are specific creatures in question who want it to hold them, like a huge ice boat or a protective dome; couldn't a creature become trapped in that afterward without the caster's intent? Are you telling me we can't have an awesome skating pool to do tricks in, just because some wimpy creature might not be able to find a way out? "This 45 degree V-shaped depression outside the ice cave is purely a decorative touch, honest." Seriously though, there could be so many uses for a 30 foot bowl!
If we can make a trench or change elevation, can we make a slide?
Raising a 15 foot by 30 foot area so that one edge of its length is 15 feet higher would make a big 30 foot wide uphill ramp, 15 feet long. Very "difficult terrain" that might even require Climbing, sure, but an icy ramp is not in itself really a trap, is it? No moving parts, nothing concealed. Even if a slide were suddenly cut right underneath an unwilling creature, I'd be hard pressed to call it "trapping" them; more like moving them. Unless there's a cliff or closed room or spikes or rabid wolves or a locked-door Vogon Poetry reading, at the bottom of the slide, I personally don't feel it's being shaped "to trap" a creature. Surely you can make a slide for yourself to slip down? (Could add at least another 30ft of travel!) YGMMV.
How about a lens?
Pure water that freezes without the introduction of bubbles can be almost optically perfect. Never mind setting creatures on fire with sunlight, what can we do with a lens up to 30x30x15 feet across? How about a skylight that creates a nice hot spot on that big rock in the center of your igloo?
I'm on a boat!
Isn't a boat just a trench with no ground beneath it? ;S Any iceberg will float, but if your GM will let you freeze some water & give it even a little bit of a raised edge, you can create a pretty large boat in a single action. A keel should be no problem, but sails are probably not included...
Didn't say anything about damage to objects.
The guys behind us have a boat? Let's scuttle it. 120 range: 30x30x30 foot mace-shaped spikey ball comes buoyantly popping up out of the water from 80 feet below their hull. Or just turn the river to ice under their boat; the creatures aren't trapped, they're free to leave their icelocked boat at any time. The enemy has barred the doors of a fort; we could try a big frosty battering ram. Leave constructs & animated objects grappled by throwing some water at their feet & freezing it. Encase them entirely in a block of ice to restrain them. See that construct 15 feet from that fountain? Looming over the construct, make a 15 foot tall hammer that immediately falls under its own weight. So long as you're not hurting a creature, it's all good! (Just try to keep the "traps" one simple shape, by my reading.)
As written, the water could still trap or damage creatures?
It says "You can change water to ice within the area and vice versa, and you can reshape ice in the area in any manner you choose." and then it says "You can’t shape the ice to trap or damage a creature in the area." (emphasis mine)... Which is NOT the same as saying 'You can't use Shape the Flowing River to trap or damage a creature in the area' or 'You can't change the water or shape the ice to trap or damage a creature in the area.' So again, YGMMV, but if we don't squint too hard at the intent, the RAW of the spell seems to indicate that you could turn a 30x30x30 area of ice into water & if that drowns an entire village, at least you weren't breaking the rules.
Murky waters? Let's get to the bottom of it... by draining a lake!
Even if you've only got the Ki to use this ability twice per short rest, each 30x30x30 foot area of water changed into a block of ice, will take a lot more than one day to melt. (By my back of the napkin math, at least 39-to-40 days per block, under average sunlit conditions!) So if the watershed of a local pond or lake produces anything less than 50,000 gallons of water per hour, a Lvl2 monk can freeze the whole lake, one block after another, until it's a collection of frozen blocks which you can reshape at least 15x30x30 feet of at a time. Clear the lake floor of water & have a look at what loot might have landed down there over the years. Of course, you can't freeze any water with a fish in it...
Oh, dam.
Of course, ice dams are famous for giving way in catastrophic floods, but as long as you leave a fish-ladder, & you don't plan on having a shattered ice wall come crashing down on anyone, the ability to freeze 30 feet of river in one action could allow a Lvl2 Monk to form an ice dam twice per short rest. That's enough to dam a river 30 feet deep and 60 feet across, with enough levee to retain 15 feet of anticipated waterlevel rise before spillover, in two turns or less! A Lvl10 Monk in a boat, working inward from the riversides could produce an ice dam 30x300 feet across and 45 feet tall in 12 seconds. The range is 120 & there is no need to see the target, just have an unblocked line of effect, so the monk could freeze a body of water 120 feet deep while standing at the surface (or 240 feet deep, from one position if submerged). And that's without moving. Are monks good at moving? ;D
Raise elevation 15 feet... per use?!?
There's no mention of any conditions on repeated use of this ability to affect the same patch of ice on subsequent rounds. So each round, a Lvl10 monk could raise a 30x30 foot area 15 feet, then another 15 feet, & another, & another. Still strictly limited in terms of action economy for use during combat, I suppose. But given a little time, imagine the fortifications around a Way of the Four Elements hidden monastery!
Glacial till can hold ancient loot.
There are a lot of artifacts which were buried under Earth's glaciers. Just imagine what you might find on Toril! A Lvl2 monk could shape & melt glacial ice to drain it away, creating an earthen-floored cavern of sizable volume to sift through, using the Ki from just 2-to-4 short rests per day. If their taskmasters kindly allow them to rest for an hour out of every two, with 2 uses per short rest for a Lvl2 monk, that's 8 uses in 8 hours. A Lvl10 monk could of course work much quicker: In one minute, a Lvl10 monk could use all 10 of their Ki points to drain ice from a space 300 feet long; then another after each short rest. Doesn't even need to be a destructive process: All the ice could be put back, as you finish dragging each area for uncovered loot! Never go ice mining by hand again.
The power of ice can split stone.
You don't need anywhere near 200,000 gallons of water to pull this one off. Again, bearing in mind that we can't use this to drop a rock fall that would trap or damage any poor little creatures below, absolutely massive sections of rock can be felled by a tiny crack spread open by freezing water. Find any little crevice that runs deep enough, get it nice & wet, then change that water into ice that widens in the crack & BAM, instant wedge. Granite cliffs a mile high can be brought down to a 30-degree-slope of rubble, if there are any cracks or crevices at all within the stone.
Move heavy objects easily!
Sisyphus should have been a monk. Getting a boulder uphill is easy! Just make sure you have plenty of water (you can move it uphill as ice, if you need to, will just take one minute & a short rest after), then flood the area around the base of the big heavy thing you need to move. You can build a retaining rim for the pool of water, out of ice, if you need to; for objects less than 30 feet across it should only take 6 seconds to create a suitable tray'o'ice to pour more water onto. Got a nice volume of water there? Great. Now freeze it, level it so the heavy thing isn't stuck in ice, & raise the elevation of the icy slope 15 feet on the downhill side. Whatever thing you just raised up, should slide down the ice a good 15-to-30 feet (or more) from where it started. Rinse & repeat! (Actually, no rinse necessary, just shape the same ice again & again until you reach the top of the hill.) Need to get it downhill? Even easier! Raise it up on some ice, shape the ice into skis, & aim it at any smooth surface. Rough surfaces can of course be leveled with more ice, if you've got enough water around.
Bring life to the desert!
In many arid, seemingly dry & lifeless regions, the water table is actually not far down, below the porous sand & rock but atop the denser strata. In places like Colorado's San Luis valley, a desert dry enough to produce sand dunes & salt flats, the water table is less than ten feet down! If there's any underground aquifer less than 120 feet underground, you can freeze & raise a column of it, 15 feet per use of this feature, to pierce the desert dust & bring life giving water up to the surface! Tap into a flow from a source uphill, & a spring will flow from the hole you create even after your ice water is gone. Otherwise, you can raise a volume of water 30 feet on a side by 15 feet per use until it surfaces. If it took you all day (or even several days!), that's still 200,000 gallons of water somebody would have had to dig a well to get to, & now those hundreds of tons are already hauled up, & can be used to freeze perishables in addition to serving as a water source.
Create a winter wonderland.
Once again, we'll need a good quantity of water to make this work, so if you've got spells or an item to create water you're already ahead here. Name one desert dwelling ruler who wouldn't want flash-frozen exotic foods, air-conditioning, ice sculptures, or a skating rink, for their daughter's birthday? A few walls of ice forming a \ / to collect the prevailing wind will provide noticeable cooling to a covered area of impressive size. Creating a skating rink is now a piece of cake, & a pillar of ice that isn't full of bubbles & cracks is just what a carver needs, to turn out breathtaking works. Any foods found in your travels can be kept on ice with almost trivial ease; handing a ruler some crazy fruit is a well-established way to get one's foot in the door of a royal court. Turning a few hundred thousand gallons of water into ice sounds like the kind of thing people in a hot climate would pay a lot of money for. Also, I'm assuming we can't shape standing water or ice into snow, because snow is a very complex shape to make... But if you know anyone who can cast Fog Cloud... Instant snowflakes!
Speaking of Fog Cloud...
If an enemy is standing in fog or mist, they're basically begging to have Shape the Flowing River used against them; but how? Well, if your GM will let you freeze fog/mist within the enemy's space, you could change all the moisture in a 30 foot area around them into ice, & shape it into a single lump around their weapon. You haven't trapped them or hurt them, but they'll have a really hard time using that bow or finesse weapon until they break the ice off it. Are they trying to use a vehicle? Denied: Freeze ice over any moving part & it won't be going anywhere. Heck, just freeze any vehicle or loose object right to the ground. Alternatively, although breakable, even the thinnest physical barrier blocks a wide variety of targeting, so a Fog Cloud that suddenly coalesces into a paper thin box around your party (with one side open?) isn't all bad, either. Since the Fog Cloud can be cast at a good distance as well, you could perhaps create a hailstorm above someone's building; or inside a grand gallery of delicate art.
Escape across water.
Need an escape route? Change water into ice & run across, then change it back to water behind you. If there's a bridge, run across the bridge, then destroy it with a pillar of ice rising from below or an iceberg flowing downstream. For extra flair, your GM might allow you to turn an area of muddy riverbottom water into ice & shape it into a tunnel under the water, so you don't have to run on ice.
Patch a hole.
Obviously when our boat/fort/barrel-of-ale is damaged, we should gather the scraps into a pile & patch the hole with pykrete, right? If it starts to melt we'll just zap it again. Good enough for now.
Manipulate the weather.
Need rain but you don't have a spell for that? If you can just get within 120 feet of a cloud, you can turn a swath of that vapor into ice, & shape that ice into an oblated teardrop so it falls right where you want it. Fall. Just before impact, shape the ice into a horizontal sheet 30 feet across (this will also abruptly slow its descent) & change the ice into water. Throw yourself at the ground and miss (this is the tricky part). Voila, a tiny patch of rain! Repeat for as much cloud vapor as you can reach with your remaining Ki. If the cloud is right overhead & it's just too hot for the cloud to rain on its own, all you have to do is freeze an area of cloud vapor & not shape the ice at all: It will precipitate out on its own as a cool rainy mist.
No, really manipulate it.
Just think of the thermal energy waiting to be exchanged between a warm 30 foot body of water and a frozen 30 foot block of ice. Aside from changing the direction of airflow within a cave system, or giving a sweaty harbor town a cool breeze for the day, a single Lvl2 monk working diligently could radically alter the thermodynamics of a respectable sized area. A small diversion of water using an ice dam here, a sheet of ice turned to water so it evaporates in the sun over there; and we've got a working salt collector. Raise a volume of water from a salt lake every day, to collect the salts in a field outside the lake bed, & in time you can transform the salted earth around the lake itself into arable soil. Cover an arctic cliff with a smooth sheet of frosty white ice to reflect precious sunlight onto the ground below, & use lenses of seamless transparent ice to refract the light at dawn & dusk; stretching out the short arctic days. Cool a scorching hot valley with pillars of ice shaped from the groundwater below or a river nearby. If you have several dedicated Lvl2 monks or one Lvl10 monk, you can shape the hydrologic & meteorologic destiny of an entire region.
Engineer an industrial revolution.
That's a lot of BTUs sent... elsewhere by a single use of this specific class feature from the "Way of the Four Elements" Monastic Tradition. I can see the marketing illusions now:
"How many times has this happened to you?" {Shows a peasant attempting to use a complicated fire and steam driven clockwork contraption, which inexplicably overheats and explodes.) "Well sweat no more, with an Icemunk™ evaporative cooling system! For just silvers a day, our speedy couriers will bring you a heat-banishing 10 pound block of 100% ice!" {Shows a Tabaxi monk with an Icemunk™ sigil brightly emblazoned across their robes, running over 400 feet, leaping over a feral dog, & dashing past impressed bystanders all in a matter of seconds, with a pack of prominently labeled ice-blocks on their back.} "With the proprietary Icemunk™ evaporative cooling system, a single block of ice can provide your wondrous items and artifacts with the arctic conditions they need to stay cool and functional. Available in multiple sizes to suit any workshop. Buy one today and get a second, half off!" {Shows a half-completed Icemunk™ kit, with pieces obviously missing.} {Shows the peasant again, sitting contentedly beneath a puffing, rattling, banging, thumping, crunching, shaking, precarious heap of kludged together machinery and adapters, with an Icemunk™ proudly perched atop. A cool drop of water drips from the oily, steaming contraption, into the peasant's cookpot below. They add a sock to the machine's churning brew, then they taste it, all the hair on their head falls out, & grows back in on their chest. They cough, and a fly comes out. A green painted whistle on the machine shrieks loudly; its noisome, smoky task finished at last.} "Dearie! Dinner's ready!" the peasant calls out happily! Then, facing the viewer: "Thanks, Icemunk™!" the peasant cheers!
"Jack and Jill can go pound sand. There's a new way to fetch water and it's super cool." Raising 13,500 cubic feet of water 15 feet upward usually takes a lot of work! That's a half thousand tons of ice lifted in 6 seconds, without exhaustion or other ill effects. Every short rest you can do this again. Just doing it once is more than most human effort could do between short rests, especially if the alternative method had been hoisting buckets. Those guys are working too hard. You can do this all day. Build a water tower (heck, if you've got enough time and water you can build the water tower out of ice: it won't melt fast enough to need more than once or twice-weekly maintenance!) & use it to power a forging hammer, a quarrying hammer, a mill, chain hoists, rope winches, or anything else that needs leverage applied. A town with pressurized running water is a town that can get more done and maybe even clean up afterward. If you're Lvl10, you've got enough uses to freeze & raise a chunk of river water, & shape it uphill 135 feet up & 135 feet over, shaped into the base of a tower. If necessary, you can shape it again later to get it up even higher. Take a rest, & after each layer of your tower is in place, repeat the process, & within one day you'll have a tower of ice big enough to hold kilotons of water. Just think of all the broken crowns you'll save yourself, & all your paying customers.
Your GM May Vary.
Reading it with a strict eye toward what not to allow, I believe the wording of this ability was written with a two-dimensional surface of water or ice in mind, rather than thinking in 3D volumes. The part about elevation says 15 feet, & while the first part's "an area of ice or water no larger than 30 feet on a side" technically means 'any shape with sides less than 30 feet across', they certainly did not intend to say that a 20 sided icosahedron of 30 foot triangles, or an amorphous polygonal form hundreds of yards long composed of 30 foot segments, are acceptable "areas".
In fact I'm pretty sure they meant a "two-dimensional area" which can have its surface shaped in any simple way. If a single contiguous surface must be maintained, that rules out all kinds of useful discrete simple objects which could be otherwise crafted of ice in a single action with this ability.
Even so, just freezing a 30x30 surface & raising it 15 feet gets you a block of ice that's over 100,000 gallons in volume. Do you know how much work it takes to raise 100,000 gallons of water even an inch? Almost all of the aforementioned examples would still work out fine (a jagged 15 foot chunk of ice popping up from below a ship will probably wreck it just fine) under most common interpretations; with one likely exception:
"Water" is probably meant to mean standing water, not mud, steam, clouds, etc. Even rain might be ruled out. That limits when where & how you can use it, a bit more, in which case all the more reason to pair it with something that lets you pull water out of a hat/pitcher/spell.
However you figure it, this ability can displace terrifying amounts of water, so don't get too hung up on talking your GM into allowing any one thing (though maybe they should) & play along with whatever ruling they'll give you. If you are creative enough with it, I'm pretty sure you'll all have fun.
I know this post is a little older, but I really wanted to throw my two cents into this. if you look at the rules as written; "As an action, you can spend 1 ki point to choose an area of ice or water no larger than 30 feet on a side within 120 feet of you. You can change water to ice within the area and vice versa, and you can reshape ice in the area in any manner you choose. You can raise or lower the ice’s elevation, create or fill in a trench, erect or flatten a wall, or form a pillar. The extent of any such changes can’t exceed half the area’s largest dimension. For example, if you affect a 30-foot square, you can create a pillar up to 15 feet high, raise or lower the square’s elevation by up to 15 feet, dig a trench up to 15 feet deep, and so on. You can’t shape the ice to trap or damage a creature in the area." It specifically says you cannot Shape the ice to trap or harm creatures, so from a DMs perspective I believe the RAW means that when you create a pillar it is not at a high enough velocity to harm someone, nor does it form around the person. So I believe if someone was floating in water and the water around them was turned into ice they would effectively be trapped, but if they are standing on top of ice you couldn't raise a pillar under them to attempt to launch them or trap them, you would simply raise them 15ft into the air. However, ignoring RAW, if there were a tunnel of ice I do not see why you couldn't close the walls together to squish an enemy, though I would add a STR check or DEX check against your monk save.
Rollback Post to RevisionRollBack
To post a comment, please login or register a new account.
I plan on playing a revised Way of the Four Elements monk (fixes most of the classes issues) for the Descent into Avernus campaign. To challenge myself, I am limiting myself to only water/ice disciplines. Before we started I used some of my gold to buy waterskins (11 total on me) and I’ll be taking Mage Initiate (Druid) for Create Water and Frostbite.
What are some creative or useful ideas you can think of for Shape Water and Shape the Flowing River?
Edit: If I were to create a wall of ice using the 5 gallons of water I have access to, should I use the Wall of Ice spell stats (8 AC / 10 hp per 5 ft of wall)?
Ice stairs/ladder.
I know a few basic including stairs, wall, slippery floor, maybe a weapon
Kind of thought about that, however, won’t that create difficult terrain? Can I even climb on those without them breaking?
Depending on its crystal structure, ice can have a shear strength over 50 PSI. So a 2 inch diameter ladder rung could support 300lb. And that strength increases exponentially, increasing diameter from 2in to 3in more than doubles it.
Slipperiness could be a concern, but the description of these techniques don't imply that the ice melts, so a rough texture on the top should provide necessary traction.
Up to DM.
The intent of Shape the Flowing River class feature for Monks of the Way of the Four Elements, seems to be simple forms:
Raise/lower ice elevation, cut/fill a trench, raise/lower a wall, or form a pillar. Note the wording on each example reads "a trench", "a wall", "a pillar", not multiples.
(It also says "The extent of any such changes can’t exceed half the area’s largest dimension. For example, if you affect a 30-foot square, you can create a pillar up to 15 feet high, raise or lower the square’s elevation by up to 15 feet, dig a trench up to 15 feet deep, and so on. You can’t shape the ice to trap or damage a creature in the area.")
I think the intent is to create one basic formation per usage of the feature. I'm not even certain stairs would qualify, though it seems reasonable in context.
That last bit about how it can't be shaped "to trap or damage a creature" worries me too:
Does that mean a bowl or funnel shape is out of the question because it could trap creatures?
What if there are specific creatures in question who want it to hold them, like a huge ice boat or a protective dome; couldn't a creature become trapped in that afterward without the caster's intent? Are you telling me we can't have an awesome skating pool to do tricks in, just because some wimpy creature might not be able to find a way out? "This 45 degree V-shaped depression outside the ice cave is purely a decorative touch, honest." Seriously though, there could be so many uses for a 30 foot bowl!
If we can make a trench or change elevation, can we make a slide?
Raising a 15 foot by 30 foot area so that one edge of its length is 15 feet higher would make a big 30 foot wide uphill ramp, 15 feet long. Very "difficult terrain" that might even require Climbing, sure, but an icy ramp is not in itself really a trap, is it? No moving parts, nothing concealed. Even if a slide were suddenly cut right underneath an unwilling creature, I'd be hard pressed to call it "trapping" them; more like moving them. Unless there's a cliff or closed room or spikes or rabid wolves or a locked-door Vogon Poetry reading, at the bottom of the slide, I personally don't feel it's being shaped "to trap" a creature. Surely you can make a slide for yourself to slip down? (Could add at least another 30ft of travel!) YGMMV.
How about a lens?
Pure water that freezes without the introduction of bubbles can be almost optically perfect. Never mind setting creatures on fire with sunlight, what can we do with a lens up to 30x30x15 feet across? How about a skylight that creates a nice hot spot on that big rock in the center of your igloo?
I'm on a boat!
Isn't a boat just a trench with no ground beneath it? ;S
Any iceberg will float, but if your GM will let you freeze some water & give it even a little bit of a raised edge, you can create a pretty large boat in a single action. A keel should be no problem, but sails are probably not included...
Didn't say anything about damage to objects.
The guys behind us have a boat? Let's scuttle it. 120 range: 30x30x30 foot mace-shaped spikey ball comes buoyantly popping up out of the water from 80 feet below their hull. Or just turn the river to ice under their boat; the creatures aren't trapped, they're free to leave their icelocked boat at any time. The enemy has barred the doors of a fort; we could try a big frosty battering ram. Leave constructs & animated objects grappled by throwing some water at their feet & freezing it. Encase them entirely in a block of ice to restrain them. See that construct 15 feet from that fountain? Looming over the construct, make a 15 foot tall hammer that immediately falls under its own weight. So long as you're not hurting a creature, it's all good! (Just try to keep the "traps" one simple shape, by my reading.)
As written, the water could still trap or damage creatures?
It says "You can change water to ice within the area and vice versa, and you can reshape ice in the area in any manner you choose." and then it says "You can’t shape the ice to trap or damage a creature in the area." (emphasis mine)... Which is NOT the same as saying 'You can't use Shape the Flowing River to trap or damage a creature in the area' or 'You can't change the water or shape the ice to trap or damage a creature in the area.' So again, YGMMV, but if we don't squint too hard at the intent, the RAW of the spell seems to indicate that you could turn a 30x30x30 area of ice into water & if that drowns an entire village, at least you weren't breaking the rules.
Murky waters? Let's get to the bottom of it... by draining a lake!
Even if you've only got the Ki to use this ability twice per short rest, each 30x30x30 foot area of water changed into a block of ice, will take a lot more than one day to melt. (By my back of the napkin math, at least 39-to-40 days per block, under average sunlit conditions!) So if the watershed of a local pond or lake produces anything less than 50,000 gallons of water per hour, a Lvl2 monk can freeze the whole lake, one block after another, until it's a collection of frozen blocks which you can reshape at least 15x30x30 feet of at a time. Clear the lake floor of water & have a look at what loot might have landed down there over the years. Of course, you can't freeze any water with a fish in it...
Oh, dam.
Of course, ice dams are famous for giving way in catastrophic floods, but as long as you leave a fish-ladder, & you don't plan on having a shattered ice wall come crashing down on anyone, the ability to freeze 30 feet of river in one action could allow a Lvl2 Monk to form an ice dam twice per short rest. That's enough to dam a river 30 feet deep and 60 feet across, with enough levee to retain 15 feet of anticipated waterlevel rise before spillover, in two turns or less! A Lvl10 Monk in a boat, working inward from the riversides could produce an ice dam 30x300 feet across and 45 feet tall in 12 seconds. The range is 120 & there is no need to see the target, just have an unblocked line of effect, so the monk could freeze a body of water 120 feet deep while standing at the surface (or 240 feet deep, from one position if submerged). And that's without moving. Are monks good at moving? ;D
Raise elevation 15 feet... per use?!?
There's no mention of any conditions on repeated use of this ability to affect the same patch of ice on subsequent rounds. So each round, a Lvl10 monk could raise a 30x30 foot area 15 feet, then another 15 feet, & another, & another. Still strictly limited in terms of action economy for use during combat, I suppose. But given a little time, imagine the fortifications around a Way of the Four Elements hidden monastery!
Glacial till can hold ancient loot.
There are a lot of artifacts which were buried under Earth's glaciers. Just imagine what you might find on Toril! A Lvl2 monk could shape & melt glacial ice to drain it away, creating an earthen-floored cavern of sizable volume to sift through, using the Ki from just 2-to-4 short rests per day. If their taskmasters kindly allow them to rest for an hour out of every two, with 2 uses per short rest for a Lvl2 monk, that's 8 uses in 8 hours. A Lvl10 monk could of course work much quicker: In one minute, a Lvl10 monk could use all 10 of their Ki points to drain ice from a space 300 feet long; then another after each short rest. Doesn't even need to be a destructive process: All the ice could be put back, as you finish dragging each area for uncovered loot! Never go ice mining by hand again.
The power of ice can split stone.
You don't need anywhere near 200,000 gallons of water to pull this one off. Again, bearing in mind that we can't use this to drop a rock fall that would trap or damage any poor little creatures below, absolutely massive sections of rock can be felled by a tiny crack spread open by freezing water. Find any little crevice that runs deep enough, get it nice & wet, then change that water into ice that widens in the crack & BAM, instant wedge. Granite cliffs a mile high can be brought down to a 30-degree-slope of rubble, if there are any cracks or crevices at all within the stone.
Move heavy objects easily!
Sisyphus should have been a monk. Getting a boulder uphill is easy! Just make sure you have plenty of water (you can move it uphill as ice, if you need to, will just take one minute & a short rest after), then flood the area around the base of the big heavy thing you need to move. You can build a retaining rim for the pool of water, out of ice, if you need to; for objects less than 30 feet across it should only take 6 seconds to create a suitable tray'o'ice to pour more water onto. Got a nice volume of water there? Great. Now freeze it, level it so the heavy thing isn't stuck in ice, & raise the elevation of the icy slope 15 feet on the downhill side. Whatever thing you just raised up, should slide down the ice a good 15-to-30 feet (or more) from where it started. Rinse & repeat! (Actually, no rinse necessary, just shape the same ice again & again until you reach the top of the hill.) Need to get it downhill? Even easier! Raise it up on some ice, shape the ice into skis, & aim it at any smooth surface. Rough surfaces can of course be leveled with more ice, if you've got enough water around.
Bring life to the desert!
In many arid, seemingly dry & lifeless regions, the water table is actually not far down, below the porous sand & rock but atop the denser strata. In places like Colorado's San Luis valley, a desert dry enough to produce sand dunes & salt flats, the water table is less than ten feet down! If there's any underground aquifer less than 120 feet underground, you can freeze & raise a column of it, 15 feet per use of this feature, to pierce the desert dust & bring life giving water up to the surface! Tap into a flow from a source uphill, & a spring will flow from the hole you create even after your ice water is gone. Otherwise, you can raise a volume of water 30 feet on a side by 15 feet per use until it surfaces. If it took you all day (or even several days!), that's still 200,000 gallons of water somebody would have had to dig a well to get to, & now those hundreds of tons are already hauled up, & can be used to freeze perishables in addition to serving as a water source.
Create a winter wonderland.
Once again, we'll need a good quantity of water to make this work, so if you've got spells or an item to create water you're already ahead here. Name one desert dwelling ruler who wouldn't want flash-frozen exotic foods, air-conditioning, ice sculptures, or a skating rink, for their daughter's birthday? A few walls of ice forming a \ / to collect the prevailing wind will provide noticeable cooling to a covered area of impressive size. Creating a skating rink is now a piece of cake, & a pillar of ice that isn't full of bubbles & cracks is just what a carver needs, to turn out breathtaking works. Any foods found in your travels can be kept on ice with almost trivial ease; handing a ruler some crazy fruit is a well-established way to get one's foot in the door of a royal court. Turning a few hundred thousand gallons of water into ice sounds like the kind of thing people in a hot climate would pay a lot of money for. Also, I'm assuming we can't shape standing water or ice into snow, because snow is a very complex shape to make... But if you know anyone who can cast Fog Cloud... Instant snowflakes!
Speaking of Fog Cloud...
If an enemy is standing in fog or mist, they're basically begging to have Shape the Flowing River used against them; but how? Well, if your GM will let you freeze fog/mist within the enemy's space, you could change all the moisture in a 30 foot area around them into ice, & shape it into a single lump around their weapon. You haven't trapped them or hurt them, but they'll have a really hard time using that bow or finesse weapon until they break the ice off it. Are they trying to use a vehicle? Denied: Freeze ice over any moving part & it won't be going anywhere. Heck, just freeze any vehicle or loose object right to the ground. Alternatively, although breakable, even the thinnest physical barrier blocks a wide variety of targeting, so a Fog Cloud that suddenly coalesces into a paper thin box around your party (with one side open?) isn't all bad, either. Since the Fog Cloud can be cast at a good distance as well, you could perhaps create a hailstorm above someone's building; or inside a grand gallery of delicate art.
Escape across water.
Need an escape route? Change water into ice & run across, then change it back to water behind you. If there's a bridge, run across the bridge, then destroy it with a pillar of ice rising from below or an iceberg flowing downstream. For extra flair, your GM might allow you to turn an area of muddy riverbottom water into ice & shape it into a tunnel under the water, so you don't have to run on ice.
Patch a hole.
Obviously when our boat/fort/barrel-of-ale is damaged, we should gather the scraps into a pile & patch the hole with pykrete, right? If it starts to melt we'll just zap it again. Good enough for now.
Manipulate the weather.
Need rain but you don't have a spell for that? If you can just get within 120 feet of a cloud, you can turn a swath of that vapor into ice, & shape that ice into an oblated teardrop so it falls right where you want it. Fall. Just before impact, shape the ice into a horizontal sheet 30 feet across (this will also abruptly slow its descent) & change the ice into water. Throw yourself at the ground and miss (this is the tricky part). Voila, a tiny patch of rain! Repeat for as much cloud vapor as you can reach with your remaining Ki. If the cloud is right overhead & it's just too hot for the cloud to rain on its own, all you have to do is freeze an area of cloud vapor & not shape the ice at all: It will precipitate out on its own as a cool rainy mist.
No, really manipulate it.
Just think of the thermal energy waiting to be exchanged between a warm 30 foot body of water and a frozen 30 foot block of ice. Aside from changing the direction of airflow within a cave system, or giving a sweaty harbor town a cool breeze for the day, a single Lvl2 monk working diligently could radically alter the thermodynamics of a respectable sized area. A small diversion of water using an ice dam here, a sheet of ice turned to water so it evaporates in the sun over there; and we've got a working salt collector. Raise a volume of water from a salt lake every day, to collect the salts in a field outside the lake bed, & in time you can transform the salted earth around the lake itself into arable soil. Cover an arctic cliff with a smooth sheet of frosty white ice to reflect precious sunlight onto the ground below, & use lenses of seamless transparent ice to refract the light at dawn & dusk; stretching out the short arctic days. Cool a scorching hot valley with pillars of ice shaped from the groundwater below or a river nearby. If you have several dedicated Lvl2 monks or one Lvl10 monk, you can shape the hydrologic & meteorologic destiny of an entire region.
Engineer an industrial revolution.
That's a lot of BTUs sent... elsewhere by a single use of this specific class feature from the "Way of the Four Elements" Monastic Tradition. I can see the marketing illusions now:
"How many times has this happened to you?"
{Shows a peasant attempting to use a complicated fire and steam driven clockwork contraption, which inexplicably overheats and explodes.)
"Well sweat no more, with an Icemunk™ evaporative cooling system! For just silvers a day, our speedy couriers will bring you a heat-banishing 10 pound block of 100% ice!"
{Shows a Tabaxi monk with an Icemunk™ sigil brightly emblazoned across their robes, running over 400 feet, leaping over a feral dog, & dashing past impressed bystanders all in a matter of seconds, with a pack of prominently labeled ice-blocks on their back.}
"With the proprietary Icemunk™ evaporative cooling system, a single block of ice can provide your wondrous items and artifacts with the arctic conditions they need to stay cool and functional. Available in multiple sizes to suit any workshop. Buy one today and get a second, half off!"
{Shows a half-completed Icemunk™ kit, with pieces obviously missing.}
{Shows the peasant again, sitting contentedly beneath a puffing, rattling, banging, thumping, crunching, shaking, precarious heap of kludged together machinery and adapters, with an Icemunk™ proudly perched atop. A cool drop of water drips from the oily, steaming contraption, into the peasant's cookpot below. They add a sock to the machine's churning brew, then they taste it, all the hair on their head falls out, & grows back in on their chest. They cough, and a fly comes out. A green painted whistle on the machine shrieks loudly; its noisome, smoky task finished at last.}
"Dearie! Dinner's ready!" the peasant calls out happily! Then, facing the viewer:
"Thanks, Icemunk™!" the peasant cheers!
"Jack and Jill can go pound sand. There's a new way to fetch water and it's super cool."
Raising 13,500 cubic feet of water 15 feet upward usually takes a lot of work! That's a half thousand tons of ice lifted in 6 seconds, without exhaustion or other ill effects.
Every short rest you can do this again. Just doing it once is more than most human effort could do between short rests, especially if the alternative method had been hoisting buckets. Those guys are working too hard. You can do this all day.
Build a water tower (heck, if you've got enough time and water you can build the water tower out of ice: it won't melt fast enough to need more than once or twice-weekly maintenance!) & use it to power a forging hammer, a quarrying hammer, a mill, chain hoists, rope winches, or anything else that needs leverage applied. A town with pressurized running water is a town that can get more done and maybe even clean up afterward. If you're Lvl10, you've got enough uses to freeze & raise a chunk of river water, & shape it uphill 135 feet up & 135 feet over, shaped into the base of a tower. If necessary, you can shape it again later to get it up even higher. Take a rest, & after each layer of your tower is in place, repeat the process, & within one day you'll have a tower of ice big enough to hold kilotons of water. Just think of all the broken crowns you'll save yourself, & all your paying customers.
Your GM May Vary.
Reading it with a strict eye toward what not to allow, I believe the wording of this ability was written with a two-dimensional surface of water or ice in mind, rather than thinking in 3D volumes. The part about elevation says 15 feet, & while the first part's "an area of ice or water no larger than 30 feet on a side" technically means 'any shape with sides less than 30 feet across', they certainly did not intend to say that a 20 sided icosahedron of 30 foot triangles, or an amorphous polygonal form hundreds of yards long composed of 30 foot segments, are acceptable "areas".
In fact I'm pretty sure they meant a "two-dimensional area" which can have its surface shaped in any simple way. If a single contiguous surface must be maintained, that rules out all kinds of useful discrete simple objects which could be otherwise crafted of ice in a single action with this ability.
Even so, just freezing a 30x30 surface & raising it 15 feet gets you a block of ice that's over 100,000 gallons in volume. Do you know how much work it takes to raise 100,000 gallons of water even an inch? Almost all of the aforementioned examples would still work out fine (a jagged 15 foot chunk of ice popping up from below a ship will probably wreck it just fine) under most common interpretations; with one likely exception:
"Water" is probably meant to mean standing water, not mud, steam, clouds, etc. Even rain might be ruled out. That limits when where & how you can use it, a bit more, in which case all the more reason to pair it with something that lets you pull water out of a hat/pitcher/spell.
However you figure it, this ability can displace terrifying amounts of water, so don't get too hung up on talking your GM into allowing any one thing (though maybe they should) & play along with whatever ruling they'll give you. If you are creative enough with it, I'm pretty sure you'll all have fun.
I know this post is a little older, but I really wanted to throw my two cents into this.
if you look at the rules as written;
"As an action, you can spend 1 ki point to choose an area of ice or water no larger than 30 feet on a side within 120 feet of you. You can change water to ice within the area and vice versa, and you can reshape ice in the area in any manner you choose. You can raise or lower the ice’s elevation, create or fill in a trench, erect or flatten a wall, or form a pillar. The extent of any such changes can’t exceed half the area’s largest dimension. For example, if you affect a 30-foot square, you can create a pillar up to 15 feet high, raise or lower the square’s elevation by up to 15 feet, dig a trench up to 15 feet deep, and so on. You can’t shape the ice to trap or damage a creature in the area."
It specifically says you cannot Shape the ice to trap or harm creatures, so from a DMs perspective I believe the RAW means that when you create a pillar it is not at a high enough velocity to harm someone, nor does it form around the person. So I believe if someone was floating in water and the water around them was turned into ice they would effectively be trapped, but if they are standing on top of ice you couldn't raise a pillar under them to attempt to launch them or trap them, you would simply raise them 15ft into the air. However, ignoring RAW, if there were a tunnel of ice I do not see why you couldn't close the walls together to squish an enemy, though I would add a STR check or DEX check against your monk save.