A pool. A pool filled with water—that's crucial. It's also gotta have NCAA-mandated dimensions (source).

Diving board. One-meter, three-meter, and platform (if necessary).

Ability to swim, or at least float. The "Sudden Urge to Jump" that Jack Sparrow seemingly lacks. 

Bathing suit. This is optional, depending on crowd and venue.

Don't be afraid to show some skin.