Please ma'am, just tighten the straps, and we won't have to sort this out downtown.
My most splendiferous sister sent me a Christmas present:

So, in celebration of my new status as Gravity Police Officer Fancypants, a public service announcement follows.
A bikini, like a bra, should offer support. It should not merely cover whatever leathery flaps happen to swing around your belly button. The tender quiver of unsupported, unnecessarily elongated boobies is enough to distract and confuse anyone. Don't be fooled - this is a national security issue. Underwire up, baby.