[Feature] Water Environment Please

[kattwalker]

Voxcad used to have a water environment. Sam seems to think there is a version of voxcraft with a simple water environment somewhere...could this be made available :)

[skriegman]

Looks like the surface friction model is only in the cpu version
https://cdorgs.github.io/code.html

If you adapt this code for gpu, please submit a pull request with a simple demo for review.

If you have trouble along the way, please submit questions here with demos that we can reproduce locally.