Get a triathlon suit.

Yes, get a triathlon suit. Regular swimsuits with mesh linings and thin straps will chew up your armpits and neck after a mile or two.

Tri suits are designed for long hours of movement without rubbing. They have flatlock seams (less friction), no mesh lining, and a snug compression fit that stays in place. You can also add body glide or chamois cream on high-friction spots like your neck, underarms, and shoulder blades.

If you really hate the look or feel of a tri suit, a one-piece square-leg swimsuit (like from TYR or Speedo) works okay, but you’ll still need to lube up. Jammers (tight, knee-length shorts) plus a rash guard is another option, but the tri suit is the most tested solution for distance.

Your shoulders will thank you.