Take the plunge and see the depths of Hawaii's undersea world. Explore ocean reefs, sea caves, swim in the company of sea turtles, monk seals and spinner dolphin. Take lessons before you come or be certified during your visit. Snorkeling is easy to learn, requiring just a mask, snorkel and fins. Hawaii's top spots include Hanauma Bay on Oahu, Kealakekua Bay on Hawaii's Big Island, Kee Beach on Kauai, Hulopoe Bay on Lanai and Molokini islet off the coast of Maui. A number of Scuba dive companies are rated five stars by PADI and can guide you on one or two tank dives to dive spots in waters off every Hawaiian island.