You're on spring break, you have had a little to drink, you are having fun, what is then more natural than to get dressed up in a bikini and walk around. It makes people laugh & talk and you get the added bonus of getting in touch with your more feminine side.
Over 150 photos
Genexion is a Flickr user who has made his collection of guys in bikinis available for your viewing pleasure:
Guys in bikinis (flickr)