You can control the watery tumult sloshing between you and the finish line without a special swimsuit in a few ways.
You can lower pressure drag by controlling how you present yourself to the water, says NASA engineer Wilkinson. It's really your vertical surfaces -- that is, those perpendicular to your swimming -- that push the water. If you dive in sleekly, keep your body in a horizontal line as you swim and don't allow your legs to sag, you've done a lot to reduce pressure drag. The water will push hard only on your head, shoulders, fingertips and feet.
You can cut wave drag starting with your dive. "You'll notice that when swimmers jump off a block, they spend an awfully long time underwater," says Wilkinson. "Underwater, they have much lower drag because there's no surface wave associated with it. So they'll try to get halfway across the pool before they come up." Once you pop up, if you float higher in the water, you'll push up a smaller wave in front of you. "Naturally talented swimmers seem to float better," says Jeremy Kipp, an assistant swimming coach at the University of Southern California.
Beyond that, get out the shaving kit. Shaving your body hair cuts drag by smoothing your surface. With less roughness, water will flow over you more easily. (Unless you're Mark Spitz; then you manage to win seven Olympic gold medals with water riffling through your mustache.)
Of course, you can also hit the gym. Strong abdominal muscles will help you stay straighter and float higher in the water, says Kipp. With a strong upper body, you can worry less about drag -- you'll compensate with more powerful strokes.
But if your technique and your body are in top form and you still want to swim faster, then someone wants to sell you a swimsuit.