Thyais Walsh, 35
Before: "Boy shorts had just come out. I'm a slave to fashion, so I had to have them," says Thyais—even though her shorts are unattractively tight at the waist and legs.
After: The vivid tank emphasizes Thyais's narrow torso, while high-cut legs on dark brown bottoms make her thighs seem leaner (Be Creative top, $48, and bottom, $38).
Confidence trick: Bring a pair of heels when you shop for swimwear—they flatter legs and inspire better posture.