Apple Watch in the pool

Yes you can swim with the watch. Water lock, locks the screen so water will not activate anything.

Also when getting out of water lock, it clears the speaker of water.

See Swim with your Apple Watch

also About Apple Watch water resistance

While Apple claims you can swim with it, I wouldn't do it if I were you as they do not back that up. I just went for a swim this past weekend and my brand new Apple Watch SE is now gunk (won't even turn on) and Apple won't cover or replace it. They DO NOT cover their devices in such circumstances unless you buy Apple Care.