Whenever me and my buddy go to play split screen the water appears a brighter blue on top but when you are underwater you can only see about 7 blocks in front of you. If you are the host of the world it doesn't happen to you but if you are the one signing in to the world for split screen the water appears brighter on top but extremely dark underneath. This bug has only recently started effecting me and i think it came with the panda update.