Ha ha... Maybe the unreleased beta has it fixed? Anyway, I do combats to check my new icons/spells fairly often, and wasn't trying to search for the bug... I just saw it twice/thrice coincidentally.
Re: combat set... Actually, making these is kind of interesting, as we can learn all sorts of things about coral, undersea life, etc....

The brain coral actually looks a bit too yellow (and it is huge, so sticks out weirdly, I think); the greenish one is the new palette (the yellow one was the original). The dark-colored pillar-things are actually pillar coral...

Not much out there to draw that is 12' high to substitute for the trees... Actually, this wilderness set was done rather haphazardly (as I want results right away!)...
One problem with deep water is that we can color it darker - but the icons themselves will still be normal color (and stick out quite a bit)... Hmm...
By the way, in the link that you gave (about adding rivers to combat), they mentioned a underwater combat checkbox that was forgotten about in FRUA or something like that?
Anyway, looking forward to see your combat set!