So I'm stumped as to how to design a humanoid water elemental that's not the usual.

[Fallen Angel]

The usual for a water genosi/elemental is 'humanoid that can survive depths that would crush a normal human'. I'm also trying to make them survive depths that are bone crushingto normal humans. (backstory: The race was genetically created so they could live deeper than even those who were 'humanoid but different in they can survive deep pressures'.) So they love depth, but can survive the surface or have some technological way to interact on the surface in surface cities. (They kind of need to because their homeworld has it's capital - and all that entrails) on a structure that floats like a iceburg. (Most underwater, some above water.) To somewhat compliment another scheme, they are also to a pershave matter related magical powers*, as it's the only of the five fields of magical power that isn't a logical fit for another group.**

*Material, Creation, Destruction, Mental, Movement.

**The four elementals and Humans Paragons are as stated below.
Fire Elemental - Destruction. In essence it's a FR Fire Genosi.
Air Elemental - Movement (or how to use air and redirection/winds to yoru advantage. They have bird like bones, they hate the water and are seen as peverse for the notion by their predecessor clade's. Same's true for the most devoted Hawk/Pheonix genotype'd.) They like staying in the air at all times, and their magical abilities are the ability to fly and produce a protective region of air aorund their bodies that where they can modify the movement properties of items.
Earth Elemental - Creation. Their skin naturally is supposed to support moss when healthy. They have vines for hair when healthy, with leaves/flowers if really healthy. They can channel life force.irss
Human Paragon - Mental. They look like the standard 'humanoid' form of the parental nation that created their clade. (Magic/Genetics.) Which is to say bluish skin with oddball hair colorations. (Green, Blue, White occasionally, Dark Red, Purple, occasional Ultraviolet shades - very much darker than black.) UV+normal eyes with hard mental blocks to keep bright light from being seen. (Anything brighter than a star in a standard Class M sky.) Internal heat regulation that can with effort as standard. Bones are thicker, with more latticework, and more strength. (As hard as bone could become without breaking Mo's Scifi Hardness Level 4/What's possible in the setting.)

[Aeolius]

If you have Stormwrack, you might incorporate blackwater into your elemental... otherwise go for an odd template. In the past I have used styx-infused, colloidal gold, and the like to add variety to water elementals.

[Rainbownaga]

Not 100% what your asking, partly because you're using a lot of jargon and 4chan doesn't seem to be online at the moment so i can't see what you're referencing.

So you've worked out they're creatures that can withstand incredible depths, far more than other creatures. They're magic is "material" whatever that is, and they may/may not have trouble with low pressures.

My thoughts immediately went to making them jelly like. They can hold a humanoid form within the water due to this, and resemble their element far more that the 'blue humans' would. On land they can wear some kind of special suit that provides them with an exoskeleton to replace the one they lack. Their control of the material may reflect their control over devices that they need to interact with humans, or it could be full-on shape-shifting.

If you mean 'design' as in stats, you can just base them off any other elemental but switch their gimmics and change any stats as needed.

[Fallen Angel]

Thank you for your comments. I apologize for the screwy OP. (The link was.. I guess my PC copied something into the post I was writing and I did not notice.)

I'll rewrite and resubmit my OP.

[Shpadoinkle]

... I didn't see the first version of your post, but I still have no idea what you're asking.

[Debihuman]

The usual for a water genosi/elemental is 'humanoid that can survive depths that would crush a normal human'. I'm also trying to make them survive depths that are bone crushingto normal humans. (backstory: The race was genetically created so they could live deeper than even those who were 'humanoid but different in they can survive deep pressures'.)

Umm, "...the bottomless ocean depths with pitiless darkness and breath-stealing pressure, these are the elements of water genasi's heart" - quote from Monsters of Faerun page 72. They can survive at any depth in the ocean already according to that quote. I fail to see why you need to genetically alter one to survive at depths that one could already survive. Of course you may have homebrewed the water genasi in your campaign so they can't survive at those depths but that's not standard.

None of the genasi have the Humanoid Type; they have the Outsider Type. When you say a water genasi is a "humanoid that can survive depths that would crush a normal human," you are only partly corrected. A water genasi may look like a human but it is not a Humanoid and shouldn't be called one.

Debby