Document water rendering modes

what even are /water [1-4]? [5-...)?
I know but only by reading the source and experimenting.

Each type of water could use a short description. A picture for the site? Description of the settings?

Start at the /water entry point and read the source to identify what modes 1–4 and 5+ represent. Document each mode with a short explanation and relevant settings, then determine how the site can include a supporting picture; done means readers no longer need source code or experimentation to understand the modes.

Written by the indexing model from the issue text.