Photo: Jonathon Kambouris

14 of 25
Old School: Bikinis are the only sexy swimsuits.

New Rule: I've always believed that a one-piece can be just as flirty as a two piece, and now it seems designers agree with me. To keep the vibe sultry, not swim team, look for peekaboo details like the mesh and cutouts on this suit.
Mossimo, $40;