Your Apple Watch is water resistant, but not waterproof. Apple Watch Ultra has a water-resistance rating of 100 meters under ISO standard 22810:2010 and is EN13319-compliant.
If you have Apple Watch Ultra, you can wear it during recreational scuba diving up to 130 feet (40 meters) and other activities like swimming, showering, and water skiing.*
Water resistance isn't a permanent condition and can diminish over time. Apple Watch can't be rechecked or resealed for water resistance.
if you have Apple Watch Ultra, you can have it turn on Water Lock automatically when it's submerged to a depth of 10cm or lower. When you finish, press and hold the Digital Crown to unlock the screen and clear any water from your Apple Watch. A series of tones plays to clear any water that remains in the speaker. For more info, see:
About Apple Watch water resistance - Apple Support
Al,so see:
Use the Depth app on Apple Watch Ultra - Apple Support