Player can move upwards in a downward bubble column

Steps to recreate:

1. Enter a downward bubble column.

2. Once you reach the bottom, shift so that you take no damage

3. Enter swim mode

4. Aim your mouse/camera upwards and press space

5. The player ascends while in a downward bubble column

This will work in both multiplayer and singleplayer, and it is not affected by whether or not the bubble column is surrounded by water.

Video taken in 1.17.0, tested and works in 1.17.1 Pre-release 1.