Devin's very rough guide for... (thread)
Simplifying Water!

Here's a bunch of little tips I've figured out from my personal water studies. Starting with the water's surface from below. My fav references for this are Ponyo and Lilo & Stitch, combined with lots of photo ref.

Water's Surface from below 2 - I recommend gathering a lot of photo reference and playing around with colors alongside shapes. often contrast of hue (greenish vs blueish) and saturation (grayer vs more saturated) will play a huge part in realism and separation of shapes.

Start looking for hints of what's behind the water's surface in your reference. You can often decipher the position of the sun & clouds through the water, although distorted.

We can also spice this up with reflections of whatever's going on in our painting using the same shapes.

Using different color combinations, we can achieve different looks with the same general shape language and pattern.

Note in the first example how we can use hue contrast rather than value contrast for a vibrant finish. The second example uses much greater value contrast.

Moving onto the surface of the water from above... the surface will be based heavily on the sky and environment.

I find all the color combinations I play around with by browsing and studying photography. Subtle value, saturation, and hue shifts make a big difference.

Next up - Bubbles. Bubbles are one of the greatest tools for achieving depth and the illusion of distance underwater.

Bubbles following motion will dictate how powerful the motion was and how much water it pushed.

Distance in water (especially murky water or choppy ocean water) can be shown via visibility falloff.

From above, anything below the water will appear to have varying degrees of water distortion. This can be shown through wavy edges to forms & color shifts.

As with everything I post, this is just my experiences and what has worked for me!
I always encourage everyone to explore these concepts through varied references and finding ways to represent them that work best for each individual!
Hope this is useful! Good luck!