I was testing out the new features and i found that part of the phantom's wings is transparent. Unfourtunatly, looking through this part of the wing renders water invisible. It may render other things invisible like nether/end portals(just a guess) but i didn't check that out.

P.S. I cann ot attatch a screenshot: your site says "An internal error has occurred. Please contact your administrator" Just put a phantom over some water to see.