Hats: Pack the most protective hat you can find that has an adjustable chin strap to keep it from blowing off your head. Alternatively, you can clip any hat to your collar with a cap retainer ($4, chums.com).
Shirts: Look for moisture-wicking, quick-drying fabrics with antimicrobial properties that cut down on odors. Some now even have cooling properties that activate when you sweat. Long sleeves protect your arms and, unlike sunscreen, won't rub off.
Shorts: Bring rugged shorts with UV protection and ample pockets. Quick-dry varieties that can also be worn as swim trunks make it easier to pack light. It's especially helpful if at least one of the pockets has a zipper so your cash doesn't fall out when you swim to the bar on the beach.
Shoes: Nonmarking soles will keep you from scuffing up the boat's decks. Mesh and other breathable fabrics allow shoes to drain water and dry quickly. Sneaker styles are comfortable and secure, while traditional boat shoes transition easily to night wear ashore.