Steps to Reproduce:

1. Enable the Short Sneak and Crawling experiment;
2. Build any setup with both water and air under a 1 block high space;
3. Crawl into the air space;
4. Hold the jump button and crawl towards the water.

Observed Results:
Once you're fully inside of the water space, you swim up and phase through the ceiling slightly, leaving you stuck in that spot. If there's lava over the ceiling, you fully leave swim mode when you touch it and that allows you to clip all the way through.

Expected Results:
Your collision stays that of 0.6 blocks high and you just swim up until you touch the ceiling, allowing you to freely roam around that space without clipping.

Screenshots/Videos attached: Yes

Notes: