Here are some further outputs from unfinished work on water, this time from the underwater environment.
A sunken ISS space station
And a short video of diving around in a small bay that shows it better. Note it's still unfinished, particularly the caustics is missing that would enhance the sense of depth.
Use caustics sparingly, they are mostly a shallow water effect that gets lost with depth very quickly. A lot of ambience under water is from the very specific light filtering, as well as floating particles and audio.