When they get to the beach, Haley and Allison say how beautiful the island is, and Kirk strips to his shorts and encourages the girls to strip.
They were surprisingly bisexual - surprising in that their passion was not revealed until about twenty minutes in the film; although it was hinted they were lusting after each other, with Allison clasping Haley's naked body.
The shark may seem lethal, but maybe he's just misunderstood—we'd chase these hotties, too.
Thing is, she knew she was gorgeous and would do anything to show it.