For now, water detection works good at sea level, but it is difficult for altitude water bodies:
If water surface is made with a full black (0x000000) color, surface becomes invisible and player can see through it up to sea level.
If water surface is made with alpha channel at 50% opacity, it is always possible to see through surface. By setting transparency detection at at least 99% opacity, surface is detected as water but it is not possible to anything trough it. Result can be checked on any altitude body of Corsica scenery update.
For now, water detection works good at sea level, but it is difficult for altitude water bodies: