Crash after jumping from mountain into water

Put the summary of the bug you're having here
We jumped from a tall snowy mountain (just above the clouds) and landed in water.

What I expected to happen was...:
We started swimming and expected to keep swimming.

What actually happened was...:
We started swimming and the game crashed and opened the crash reporter.

Steps to Reproduce:
1. Go to a mountain higher than the clouds
2. Jump straight down into water.
3. ???
4. Crash