When flying an elytra into water blocks, the player model's arms and legs begin flailing wildly.

What I expected to happen was...:
The player model would transition from the flying animation to the swimming animation and also give a boost in speed through the water (similarly to when the player walks off a block and into water).

What actually happened was...:
The player model remained in the flying pose and the arms and legs moved rapidly and uncontrollably. After a while, the flailing stopped, but the player model stayed in the flying position. When I moved the player, the limbs started flailing again.

Steps to Reproduce:
1. Put on an elytra
2. Use it to fly directly into water
3. The player model's limbs should start to spasm wildly