On your body: A life jacket, of course. Kayakers wear special short lifejackets that do not impede movement. Make sure yours is fitted right. Recreational boaters–people sticking to flat water–can get by with swimming suits, shorts, a hat and old sneakers. Whitewater boaters are pretty geared up, with fast-drying, sun-blocking warm weather clothes or insulating, waterproof colder weather clothes.
On your head: Most clubs require helmets for whitewater trips, with good reason. They save your brains. Sooner or later, you’ll hit or scrape a rock. Some people wear helmets with face guards.
On your feet: Boating shoes, usually neoprene with rubber bottoms, which protect your feet from rocks and provide some grip in case you need to portage or walk through rocky river bottom.