Apple

I have the Apple Watch Ultra. I currently don’t use it in water at all. I will occasionally turn on the water mode thing in the task bar if I have to walk into the store etc and it is raining bad. My mom has mobility issues and wants to start walking in a pool a few times a week, I said I would go with her. Can I turn on the water mode thing in the task bar and have my arm/wrist under the water the whole time while we walk to track my heart rate etc (I have POTS, I have to keep track of it) without it ruining my watch. I am scared of ruining the watch. It is the most expensive thing I own and I am still paying it off in monthly payments. Is this really water proof? Like walking in a pool for an hour while my wrist is under water the whole time? Thanks in advance for calming my fears, lol.