Shipwrecked in Saltmarsh

DC 14 Con saves:  4,  1.

 A thunderous blast erupts from the piled cargo near the port hull. Everyone reels from the blast, debris flies, and the already-sloshing water vibrates. Both nearby corpses stagger from the explosion. (They are both seriously wounded, but not down.)

The hull buckles slightly, and seawater sprays in. The already slowly-sinking ship has sprung a significant new leak.

Dain, and Katernin (protected) may act next.
Kelnan, Katernin, and Dain should roll a Dex Save as well (and if Kelnan rolls below 8, he falls through the hatch.)

Kelnan

Dex save: 21

Kelnan stops himself from being thrown down the hatch by whatever hit the ship (and immediately afterward ducks from the loud concussion below.)

Dain, prone near Kelnan, is in no danger from either event.

Katernin, facing a corpse below, tries to hang on: Dex Save: 18

 ...and does. 

Katernin and Dain are up - both are in melee range of #1

Katernin and Dain may act next. Both are in melee range of the staggering corpse under the hatch. It is seriously wounded by Molo's blast, but still standing, and still enraged by Katernin's turning attempt. Meanwhile, seawater continues to spray from the failing starboard hull, and the water inside the hull is still jostling back and forth from whatever struck the hull on the same side moments ago.

From above, Dain makes a wild swing at corpse #1 with his maul:
Maul Attack vs. Corpse #1:  24. Bludgeoning Damage: 5

He very nearly beheads the unearthly thing, but it still comes at Katernin.

Katernin responds with a deft swing of her Handaxe:
Attack: 19 Slashing Damage: 3

While her spectral whip lashes at it:
Attack:  13  Force Damage: 11

 And with that, Katernin's ghostly whip finishes what Molo and Dain started. The undead corpse falls beneath the fetid waters. #1 is down.

#2, distracted by Fianna's appearance, turns its attention from Molo to her:
Claws Attack vs Fianna: 14  Hit: 13 slashing damage (and a DC 10 Constitution saving throw or be paralyzed.)

Kelnan is up next! 

9 - Fianna's Con save vs paralysis.

     Fianna is feeling a bit still from this battle, it seems...

Fianna topples into the churning waters, unable to move. (She has a lungful of air, and a hearty constitution, so she will last a full three minutes floating in the foul waters of the hold.)

Kelnan is up!

Kelnan, still concentrating upon his protection spell on Katernin, is up next. He can just see the corpse menacing Molo and Fianna.

Kelnan summons up his power and launches a crackling Chromatic Orb at #2 hoping to finish it off and let work proceed before the ship gives way to the ocean.

Attack: 8 Damage: 15 (Cast at level 2, lightning damage)

Kelnan lobs a brilliant blue ball of electrical fluid at the undead creature, but it misses. Molo feels the uncomfortable buzz of the electrically-charged magical orb hitting the water.

A sudden shriek of splintering wood fills the air, as parts of the hull give way, not only in the hold, but also on the deck Dain and Kelnan share. Massive tentacles begin to snake in, thrashing and grasping as they start to fill the cabin. (It will take another round before they are in danger of reaching any of the party.)

Dain, Fianna (and Di'Finella), Katernin, and Molo may act next.

The ship is actively beginning to sink, as well.

     The fudge?!? Fianna thinks as loud as she can. Tentacles????

     As paralyzed as a 12 year old playing at Light as a Feather, Stiff as a Board at a slumber party, Fianna can do naught else but watch in horror and try to break out of her condition...  ((And wonder how many of you even know Light as a Feather, Stiff as a a Board...))

Con Save on fresh post otherwise I'm getting that "Potentially manipulated warning..."  12 <- Con save to break paralysis...

Molo tries to grab the box and run

Dain tries to cave the head of the nearest corpse in!

Bonus action:   RAGE!   (last one of the day)
Action:   Recklessly power attack #2:   Attack: 15 Damage: 24
Move:  Stand up from prone.

Dain pulls himself up and jumps down into the churning hold. He barely makes it through the deep, sloshing water - nearly up to his shoulders - to the foul corpse menacing Molo and Fianna, before delivering a fatal blow to the horrid dead thing. 

Combat is over for this round, but we are going to continue initiative order, as time is becoming short, and the tentacles are about to strike.  (Also: once the minute is up, the turning will end on the last corpse.)

Fianna comes to, coughing and choking.

Movement: Movement is becoming even trickier as the ship begins to rock back and forth from the movement of the massive tentacles. Climbing the rope (or stairs) will now require a DC 10 Strength (Athletics) check, unless you have a climbing speed. On a failed check, a character falls prone in the space where the climb began. The floor is now difficult terrain (and the flooded hold remains difficult terrain to everyone but Molo, who is swimming.)

Moving the box: The box is bulky and hard to handle. And since the tentacles arrived and the ship started pitching and flooding, the box has become even more awkward to move.
One or two characters can try to carry the box. A character can use an action to pick up the box or pass it to someone else with a successful DC 12 Strength (Athletics) check. On a failed check, the character drops the box. How fast someone moves with the box is based on their Strength score. If two characters carry the box, the total of their Strength scores determines how fast they can move. 

Molo finds that assuming he can even grab the awkward box (go ahead and make that DC 12 Athletics check if you're ready), he'll only be able to move it 5 feet per round while swimming (and he expects won't be able to carry it at all on his bum foot once he reaches solid floor again.)

Meanwhile the massive, menacing tentacles puncturing the side of the vessel continue to snake in. They will reach you next turn.

 Katernin and Kelnan can act, and Molo can finish his turn. The rope is still secured around the box, and the other end tied to the mast on the deck above near Kelnan, but the rope is currently unattended and slack.

Kelnan tries to get a view of the box and says a few words to cast Knock, hoping the thing can be opened and make its content easier to escape with.

He then moves to the side opposite the advancing tentacles and tries to assist his compatriots in climbing from the hold.

(Are the stairs we took in blocked by the tentacles entirely? Or might it be possible to get past them?)

With a loud "pop", the top of the crate suddenly flies open. Inside, packed with a little straw, is a large, seamless, blue metal cube. It's slightly smaller and lighter than the crate, but its smooth sides make it no less cumbersome to move. Whether you carry the crate or the cube, your movement penalty is unchanged. This does, however, confirm its contents - this is definitely the box Aubreck hired you to retrieve.

The tentacles are moving and thrashing wildly, smashing and crushing and scraping whatever they can reach. (The tentacles in the map are illustrative only - they are constantly moving, and all over the place. One can climb those stairs, but by next round, nobody will be safe from these things anywhere on the ship. One place will be as good as the next to dodge them)

Katernin may act, and Molo can finish whatever he's doing. Anyone trying to climb the rope out of the hold must roll a DC 10 Strength (Athletics) check with advantage (due to Kelnan's assistance.)

Molo fumbles the cube out and carries towards the stairs, while whistling a tune to draw everyone’s attention, hopefully inspiring Fianna. D6
athletics 19 

Dain, in a fit of rage will swing his huge maul at the tentacles nearest Molo, trying to keep their attention away from the little kobold who is carrying the cube.

Move:  if needed close on the nearest tentacle to Molo~
Action:  Normal Attack (not recklessly or powered as I'm trying to stay alive!):  Attack: 18 Damage: 19

Molo hefts the strange, huge, blue cube and begins to swim with it - slowly - toward the hatch. 

(Katernin still has an action if she wants to use it.)

The tentacles have fully filled both decks. They thrash and batter the interior of the ship, smashing holes and tearing away at anything and everything it touches. The tentacles strike quickly, spearing through the sides of the ship. Only luck can save your characters from being hit by them. From here on, at the start of your character’s turn, make a DC 10 Dexterity saving throw. On a failed save, that character takes 2d6 bludgeoning damage from the tentacles’ frantic thrashing.

Everyone may act. (Fianna has d6 inspiration. Molo is no longer poisoned. Kelnan is still concentrating on Katernin's protection until you tell me otherwise. Katernin may take an extra action prior to the tentacle strike.)

I'll roll for Dain: DC10 Dex Save: 8

Successfully dodging them, Dain takes a wild swing at the tentacles, accomplishing little. (But I'll grant Molo advantage on his next dex save, due to Dain's efforts.)