Speedo's Core Stabilizer suit, $98 (speedousa.com)
WHAT IT IS: A swimsuit constructed with the same NASA-designed precision as Michael Phelps' super-skintight number, but comfier (this amateur version boasts a knit fabric that has more give than that of the pros').
WHAT IT DOES: Its girdled core region keeps hips afloat for less drag and speedier stroking.
THE RESULT? A more efficient workout.
WHAT WE LOVE: The belly-flattening silhouette—and the bust-supporting, sewn-in sports bra.