The Elder Guardian pathfind is broken, he usually can't find an accessible path to swim and ends up swimming against the wall or simply stay spinning randomly.

Steps to Reproduce:
1. Create a new world in creative mode.
2. Use /locate to find the coordinates of an ocean monument.
3. With the coordinates, teleport to the ocean monument.
4. Go to the Elder Guardian's room.

Observed Results:
You will notice that the Elder Guardian cannot find a pathfind accessible to swim, so he will try to swim against the walls, or will it spin randomly.

Expected Results:
The Elder Guardian should have an improved pahfind. That is, he should stop trying to swim against paths inaccessible for his size.

I have attached two videos as an example below.