Never, ever swim alone. If you don't have anyone to swim with, try placing a personal ad that says you're looking for someone to get wet with.

Clerics and magic-users (third-level or higher) can use their Protection From Energy spell to combat the effects of the sun. The rest of you peasants will either need to find a Scroll of Protection or cough up enough platinum pieces to buy some sunscreen.

Alcohol dehydrates the body, which is why it's such a good idea to drink beer at the beach – there's nothing like a good swim to hydrate the body after you've drank yourself stupid.