If you noclip while in a water volume, you no longer collide with anything but remain swimming (rather than entering the noclip movement mode). On exiting the water volume, you enter the normal walking movement mode, but also without collision.
Steps to Reproduce
Noclip while in a water volume.
What I expected to happen
The player enters the noclip movement mode.
What happened
The player remains in the swimming movement mode but no longer collides with objects (other than other water volumes).