In Minecraft Java 1.16.3.
Dig a 3x1x1 pit in the ground.
At the bottom place a fence
Place a water source above the fence
Leave air above the water source
Spawn rabbit inside that hole
What I expected:
Rabbits jump while inside the single water source bock.
What happened:
Some rabbit stuck in the north west corner of the water block above the fence stop jumping and drown in the water.
This appears to be a duplicate of MC-150224, which hasn't yet been resolved. If you have any additional information to provide regarding this issue, feel free to comment on the parent ticket. If you feel that this issue is affecting you, feel free to vote for the duplicated ticket, to give Mojang a basic idea of how many people are impacted by the problem. Just to further inform you, this will not determine how quickly the bug gets handled or fixed.