Water Sports

Lanai has Hawaii's best water clarity because it lacks major development, it has low rainfall and runoff, and its coast is washed clean daily by the sea current (known as "The Way to Tahiti"). But the strong sea currents pose a threat to swimmers, and there are few good surf breaks. Most of the aquatic adventures -- swimming, snorkeling, scuba diving -- are centered on the somewhat protected south shore, around Hulopoe Bay.

The only outfitter for watersports is Trilogy Lanai Ocean Sports (tel. 888/MAUI-800 [6284]; www.visitlanai.com).

Sailing & Snorkeling

Trilogy Lanai Ocean Sports, which has built a well-deserved reputation as the leader in sailing/snorkeling cruises in Hawaii, offers both a morning and an afternoon snorkel sailing trip on board its luxury custom sailing catamarans or its 32-foot jet-drive rigid aluminum-inflatable vessel. The trips along Lanai's protected coastline sail past hundreds of spinner dolphins and into some of the best snorkeling sites in the world for $203 (half-price for children 3-15) and include lunch, sodas, snorkel gear, and instruction.

If you just want to snorkel on your own, Hulopoe is Lanai's best snorkeling spot. Fish are abundant in the marine-life conservation area. Try the lava-rock points at either end of the beach and around the lava pools.

Scuba Diving

Two of Hawaii's best-known dive spots are found in Lanai's clear waters, just off the south shore: Cathedrals I and II, so named because the sun lights up an underwater grotto like a magnificent church. Trilogy Lanai Ocean Sports offers several kinds of sailing, diving, and snorkeling trips on catamarans and from its new 32-foot high-tech jet-drive ocean raft. It has its own version of "sunrise services" at the Cathedrals -- not only is this the best time of day to dive this incredible area, but there also are virtually no other dive boats in the water at this time. Cost is $169 to $199 for a two-tank dive, $79 for nondivers. Beach dives are available for $95 (one-tank dive) for certified divers and $95 for an introductory dive for noncertified divers.

Sportfishing

Spinning Dolphin Charters of Lanai (tel. 808/565-7676; www.sportfishinglanai.com) offers sportfishing on a 42-foot Hatteras boat. It will take up to six passengers for $700 for 4 hours ($110 for each additional hour), or you can share a boat for $150 each for 4 hours.

Surfing

If you've ever wanted to learn how to surf, let instructor Nick Palumbo, a surfing champion, take you on a four-wheel-drive surfing safari to a secluded surf spot. He'll have you up and riding the waves in no time. His Lanai Surf School & Surf Safari (tel. 808/565-7258; www.lanaisurfsafari.com) offers a package that includes a 2 1/2-hour lesson with surfboard, four-wheel-drive transportation, refreshments, and "a really good time" for $185 per person.

Whale-Watching

During whale season, from December to April, Trilogy Lanai Ocean Sports takes passengers out on its 26-passenger, rigid-hulled inflatable boat, a 32-foot jet-drive Zodiac named Manele Kai, for a 2-hour ocean adventure that explores some of the remote and unspoiled sites in Hawaii. Lanai is also home to one of Hawaii's largest schools of spinner dolphins and a haven for North Pacific humpback whales. The captains and crew are Certified Island Naturalists who make each trip educational as well as entertaining, and they can usually find these wonderful and playful mammals. The cost is $75 (half-price for children 3-15), which includes soft drinks.