Camera is put in the ground when riding a Minecart in swimming state

This post on Reddit shows the bug in action. I don't think I need to make this a private report because the exploit has already been shared on Reddit.

Steps to reproduce:

1. Place down a rail with a Minecart on it.
2. Create a 1-block tall space and enter it using a trapdoor or another method.
3. While in the swimming/crawling state, enter the Minecart.
4. Press 'W' to move the Minecart off the rail. The camera will be positioned in the ground and you will be able to easily find caves this way.