Hanauma Bay (Oahu): It can get crowded, but for clear, warm, calm waters, an abundance of fish that are so friendly they'll swim right up to your face mask, a beautiful setting, and easy access, there's no place like Hanauma Bay. Just wade in waist-deep and look down to see more than 50 species of reef and inshore fish. Snorkelers hug the safe, shallow inner bay -- it's like swimming in an outdoor aquarium. Serious divers shoot "the slot," a passage through the reef, to enter Witch's Brew, a turbulent cove.

Kahaluu Beach (Big Island): The calm, shallow waters of Kahaluu are perfect for beginning snorkelers or those who are unsure of their swimming abilities and want the comfort of being able to stand up at any time. The sunlight through the shallow waters casts a dazzling spotlight on the colorful sea life and coral formations. If you listen closely, you can actually hear the parrot fish feeding.

Kealakekua Bay (Big Island): Mile-wide Kealakekua Bay, at the foot of massive U-shaped sea cliffs, is rich with marine life, snorkelers, and history. A white obelisk marks the spot where, in 1778, the great British navigator Capt. James Cook, who charted most of the Pacific, was killed by Hawaiians. The bay itself is a marine sanctuary that teems with schools of polychromatic tropical fish.

Molokini (Maui): The islet of Molokini is shaped like a crescent moon that fell from the sky. Its shallow concave side serves as a sheltering backstop against sea currents for tiny tropical fish; its opposite side is a deep-water cliff inhabited by spiny lobsters, moray eels, and white-tipped sharks. Neophyte snorkelers should report to the concave side, experienced scuba divers the other. The clear water and abundant marine life make this islet off the Makena Coast one of Hawaii's most popular dive spots, so expect crowds.

Kee Beach (Kauai): Where the road ends on the North Shore, you'll find a dandy little reddish-gold-sand beach almost too beautiful to be real. It borders a reef-protected cove at the foot of fluted volcanic cliffs. Swimming and snorkeling are safe inside the reef, where long-nosed butterfly fish flitter about and schools of taape (bluestripe snapper) swarm over the coral.