High-waist plus halter is the vintage shortcut.

Pair your high-waisted bottoms with a halter top and you’re already 90% of the way there. That combo is basically the uniform of 1950s beach photos.

Everything else is just details. Stick with solid colors or small polka dots, skip the neon prints. Add cat-eye sunglasses and a wide-brim straw hat if you want to push it further. Hair in a bandana or victory rolls seals the deal, but don’t overthink it — the silhouette does the heavy lifting.

The shoes don’t matter since you’re at the pool.