Plenty of people brag about shark cage diving, but here's your chance to swim freely with these ancient predators! Hawaii Adventure Diving puts a maximum of six snorkelers in the water, accompanied by a dive master, scuba instructor, and a certified underwater naturalist. "We most often see three to six-foot-long sandbar sharks," explains guide Crys Hu. "And also Galapagos sharks that can reach nine or ten feet." When potentially aggressive tiger sharks swing by, guests climb back into the boat. "We have a 100% safety record. It can seem very scary if you've never swum with sharks before. But they're so calm and doing their own thing. It helps people relax quickly."