I can’t waterproof my Apple Watch

Apple Watches are always water resistant, but you can put it into a water mode where it ignores the side buttons and screen touches caused by swimming and splashing water. This does NOT change the water resistance, it just makes sure you do not accidentally make phone calls or change other settings of your Apple Watch.

There are Apple Watch cases that report to be waterproof if you are serious about waterproofing your Apple Watch.

But first I would suggest reading the webpage AppleJack has provided.

Water resistance is something intirely different from water proof.

See the link fieryjack shared on water resistance

Apple Watches are not and cannot be waterproof,see this page;

About Apple Watch water resistance