In a top, don't be tempted to go too small: Spillage along the sides will just make the chest look bigger. And keep in mind that suits run about two sizes smaller than your clothing size (honest). An underwire or built-in bra gives structure and support. You can also seek out bra sizing in bathing suit tops for a more accurate fit.

And when you're trying on either one- or two-pieces, make sure that the straps aren't a major source of support. They should serve more to prevent sag.

A few styles that aren't likely allies? Strapless bandeaus, keyholes, string bikinis and demi-bra styles.

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