It’s not what you think.

By Rebecca Daly
Updated June 09, 2016
Color block bathing suit
Credit: Roland Bello/Set Design by Jeffrey W. Miller/Soft Styling by Mariana Vera

You carefully comb the racks of your favorite store looking for a pretty print, a flattering silhouette, and a few back-up sizes just in case a particular brand doesn’t fit the way you expect. Once in the dressing room, you pull on that promising suit, and—voila!—not only does it fit, it looks even better than you expected. All done, right? Wrong.

Just because your suit looks sweet while you’re standing still in front of the mirror doesn’t mean it’s going to fit flawlessly while you’re in motion—and, let’s face it, when there’s nothing but that swimsuit between you and the world, you definitely want it to stay put. So, go ahead and move around a little bit.

These tips (you can do them all in the privacy of your dressing room) will help the next time you’re in try-on mode:

Color block bathing suit
Credit: Roland Bello/Set Design by Jeffrey W. Miller/Soft Styling by Mariana Vera

For Strapless Styles

Reach down to touch your toes, then stand back up and raise your arms over your head. If everything stayed in place and you didn’t feel the need to tug or readjust the bust or neckline, you’ve got a winner. If not, you may need to try a different size or a style with a little more security, like stay-put silicon-lined trim.

For Bottoms

Drop into a lunge position, and try a few squats as well. Every suit will shift a little, but you shouldn’t get too much movement—or a wedgie.

For Styles With Thin Straps

You don’t have to reenact gym class for this one. First, double check that the straps aren't too tight or digging into your skin. Then, try a few everyday movements—bend down as though you're tying your shoe, reach each arm up as if you're getting something off of a high shelf, and slip your bag on and off each shoulder. The straps should stay in place, just like a bra.

For Styles That Tie

This seems like a no-brainer: You want the straps to stay tied. For string bottoms, repeat lunges and squats. For string tops, test out all of the everyday movements above. If the material is too slippery to hold a knot throughout all of this, buyer beware!