Any clues how it can be done? Most of what i've found elsewhere is using hacks to look good.
Use your imagination. IMO the underwater areas in EFU are good enough.
Some overrides might help.
Use blueish fog and the desert tileset.
Try to do it with your effort, utilizing your efforts would give you the lot of pleasure. If some one helps you in case that even also good. But try to utilize your own skills buddy.