So if a creature were to be inside the area of the water wall hit by a cold damage spell (and therefore frozen solid) would that creature then be partially/fully encased in ice? And if so, what damage/conditions would that cause on the frozen creature?

Quote from BLARP666 >>

So if a creature were to be inside the area of the water wall hit by a cold damage spell (and therefore frozen solid) would that creature then be partially/fully encased in ice? And if so, what damage/conditions would that cause on the frozen creature?

 
https://www.dndbeyond.com/sources/dmg/running-the-game#UsingandTrackingConditions

DM fiat. As 3rd level spell, I can see the target being paralyzed while encased in ice, with a successful Strength saving throw against the spell save DC to break free (repeat save at the end of each of the frozen creature's turns). 

Why does the spell specify that ranged attack rolls have disadvantage if they pass through the wall? Does that mean that the wall neither blocks LoS nor provides any semblance of cover?

The wall is, at most, one foot thick whether its a straight line of a circle. The spell doesn't say the water is opaque, and I imagine you and anything / anyone in it would basically be blurry shapes that someone can try to hit, hence the disadvantage. If the wall was perfectly clear, an arrow would lose momentum or be thrown off course, once again maintaining that disadvantage.

However, the cantrip Shape Water specifically lets you change opacity, color, or freeze water. If you freeze the water yourself, someone can use that as cover until it is broken by an attack and keep repeating that process. Seems like a great combination.

Casting word is:

Facadicus Liquidium

If you bless it then wouldn't it be a wall of holy water?

The "Ceremony" spell actually defines how holy water is created. It takes an hour of time spent on a magical ritual to make a single vial of water holy water, so probably wouldn't do much to this spell's effect. 

But if you know you're going into a fight and have 24 hours to prepare, a Cleric could probably hallow (5th level spell) a pool of water that already exists, and you might be able to do some fun stuff with slinging that pre-existing holy water around the area if your DM is feeling generous.

Quote from TheMercurialist >>

The "Ceremony" spell actually defines how holy water is created. It takes an hour of time spent on a magical ritual to make a single vial of water holy water, so probably wouldn't do much to this spell's effect. 

But if you know you're going into a fight and have 24 hours to prepare, a Cleric could probably hallow (5th level spell) a pool of water that already exists, and you might be able to do some fun stuff with slinging that pre-existing holy water around the area if your DM is feeling generous.

 just saying holy water in phb also says that to make holy water you need water and 25 gold worth of silver dust which mixed with the water makes holy water.

Useful against a fire dragon, maybe? Ready action to cast it over the dragon's mouth when the dragon uses its breath weapon. Fire damage passing through the wall is halved, and then halved again from fire resistance (absorb elements, potions etc)

Quote from Akamoria >>

Useful against a fire dragon, maybe? Ready action to cast it over the dragon's mouth when the dragon uses its breath weapon. Fire damage passing through the wall is halved, and then halved again from fire resistance (absorb elements, potions etc)

 Brilliant. Absolute genius.

Question... If my party was trapped in an oceanside cave, and the tide was coming in, could a wall of water block the tide from getting in? At least temporarily until we figure out an actual plan?

Anything not covered under the spell description is subject to DM's interpretation. In any case D&D is not a physics simulator if that's what you're looking for in an answer.

I just like to try and think outside the box when spells are used

Why can't you make a dome with this spell?

Personally, I think the spell not being added to the Warlock's Water Genie spell list is a bit of missed opportunity.

Quote from Akamoria >>

Useful against a fire dragon, maybe? Ready action to cast it over the dragon's mouth when the dragon uses its breath weapon. Fire damage passing through the wall is halved, and then halved again from fire resistance (absorb elements, potions etc)

 You can’t target a dragons mouth (per the general spellcasting rules for targets) and the spell notes it has to be a point on the ground regardless. 

It's unlikely you'd even know when the dragon can use their breath next. 

The ocean would run into difficult terrain.