Oahu has a wealth of watersports opportunities, whether you're a professional surfer braving giant winter waves on the North Shore, or a recreational water-skier enjoying the calm waters of Hawaii Kai. You can kayak from Lanikai Beach to the Mokulua Islands or float above Waikiki on a parasail as a speedboat tows you blissfully through the air. If you have something of an adventurous spirit, you might scuba dive the walls of the Kahuna Canyon, swim with clouds of ta'ape (butterflyfish), or view an occasional shark from the comfort of a passenger submarine. No matter what your aquatic interests are, whether you're a beginner or an expert, you can find the right sport on Oahu.

If you want to rent beach toys (like a mask, snorkel, and fins; boogie boards; surfboards; kayaks; and more), check out the following Waikiki rental shops: Snorkel Bob's, on the way to Hanauma Bay at 700 Kapahulu Ave. (at Date St.), Honolulu (tel. 808/735-7944; www.snorkelbob.com); and Aloha Beach Service, in the Sheraton Moana Surfrider Hotel, 2365 Kalakaua Ave. (tel. 808/922-3111, ext. 2341), in Waikiki. On Oahu's windward side, try Kailua Sailboards & Kayaks, 130 Kailua Rd., a block from the Kailua Beach Park (tel. 808/262-2555; www.kailuasailboards.com). On the North Shore, get equipment from Surf-N-Sea, 62-595 Kamehameha Hwy., Haleiwa (tel. 808/637-9887; www.surfnsea.com).

Boating

A funny thing happens to people when they come to Hawaii: Maybe it's the salt air, the warm tropical nights, or the blue Hawaiian moonlight, but otherwise-rational people who have never set foot on a boat in their life suddenly want to go out to sea. You can opt for a "booze cruise" with a thousand loud, rum-soaked strangers, or you can sail on one of these special yachts, all of which will take you out whale-watching in season (roughly Dec-Apr).

Bodyboarding (Boogie Boarding)/ Body Surfing

Good places to learn to bodyboard are in the small waves of Waikiki Beach and Kailua Beach, and Bellows Field Beach Park, off Kalanianaole Highway (Hwy. 72) in Waimanalo, which is open to the public on weekends (from noon on Fri to midnight on Sun and holidays). To get here, turn toward the ocean on Hughs Road, then right on Tinker Road, which takes you right to the park.

Ocean Kayaking

For a wonderful adventure, rent a kayak, arrive at Lanikai Beach just as the sun is appearing, and paddle across the emerald lagoon to the pyramid-shaped islands off the beach called Mokulua -- it's an experience you won't forget. Kayak equipment rental starts at $10 an hour, or $37 for a day. In Waikiki, try Prime Time Sports, Fort DeRussy Beach (tel. 808/949-8952); on the windward side, check out Kailua Sailboards & Kayaks, 130 Kailua Rd., a block from Kailua Beach Park (tel. 808/262-2555; www.kailuasailboards.com). On the North Shore, contact Waimea Falls Park, 59-864 Kamehameha Hwy., Haleiwa (tel. 888/973-9200 or 808/638-8511), which also has guided kayak tours in the stream for $35 for 1 hour and in the ocean for $45.

First-timers should go to Kailua Sailboards & Kayaks, 130 Kailua Rd., in Kailua (tel. 808/262-2555; www.kailuasailboards.com), where the company offers a guided tour with the novice in mind in a safe, protected environment. Included in the tour are lunch, all equipment, and transportation from Waikiki hotels for $79.

Scuba Diving

Oahu is a wonderful place to scuba dive, especially for those interested in wreck diving. One of the more famous wrecks in Hawaii is the Mahi, a 185-foot former minesweeper easily accessible just south of Waianae. Abundant marine life makes this a great place to shoot photos -- schools of lemon butterflyfish and taape are so comfortable with divers and photographers that they practically pose. Eagle rays, green sea turtles, manta rays, and white-tipped sharks occasionally cruise by as well, and eels peer out from the wreck.

For nonwreck diving, one of the best dive spots in summer is Kahuna Canyon. In Hawaiian, kahuna means priest, wise man, or sorcerer; this massive amphitheater, located near Mokuleia, is a perfect example of something a sorcerer might conjure up. Walls rising from the ocean floor create the illusion of an underwater Grand Canyon. Inside the amphitheater, crabs, octopuses, slippers, and spiny lobsters abound (be aware that taking them in summer is illegal), and giant trevally, parrotfish, and unicorn fish congregate as well. Outside the amphitheater, you're likely to see an occasional shark in the distance.

Since Oahu's best dives are offshore, your best bet is to book a two-tank dive from a dive boat. Hawaii's oldest and largest outfitter is Aaron's Dive Shop, 307 Hahani St., Kailua (tel. 808/262-2333; www.hawaii-scuba.com), which offers boat and beach dive excursions off the coast. The boat dives cost from $115 per person, including two tanks and transportation from the Kailua shop. The beach dive off the North Shore in summer or the Waianae Coast in winter is the same price as a boat dive, including all gear and transportation, so Aaron's recommends the boat dive.

In Waikiki, South Sea Aquatics, 2155 Kalakaua, Suite 112 (next to Planet Hollywood; tel. 808/922-0852; www.ssahawaii.com), features two-tank boat dives, with transportation to and from Waikiki hotels, for $80 without gear and $96 with all equipment. On the North Shore, Surf-N-Sea, 62-595 Kamehameha Hwy., Haleiwa (tel. 808/637-9887; fax 808/637-3008; www.surfnsea.com), has dive tours from the shore (starting at $65 for one tank), from a boat ($110 for two tanks), and at night ($100 for one tank). Surf-N-Sea also rents equipment and can point you to the best dive sites in the area.

Another great resource for diving on your own is the University of Hawaii Sea Grant's Dive Hawaii Guide, which describes 44 dive sites on the various Hawaiian islands, including Oahu. Send $2 to UH/SGES, Attn: Dive Guide, 2525 Correa Rd., HIG 237, Honolulu, HI 96822.

Experiencing Jaws: Up Close and Personal

You're 4 miles out from land, which is just a speck on the horizon, with hundreds of feet of open ocean. Suddenly from out of the blue depths a shape emerges: the sleek, pale shadow of a 6-foot-long gray reef shark, followed quickly by a couple of 10-foot-long Galapagos sharks. Within a few heartbeats, you are surrounded by sharks on all sides. Do you panic? No, you paid $120 to be in the midst of these jaws of the deep. Of course, there is a 6-foot by 6-foot by 10-foot aluminum shark cage separating you from all those teeth.

It happens everyday on the North Shore Shark Adventure (tel. 808/256-2769; www.hawaiisharkadventures.com), the dream of Captain Joe Pavsek, who decided, after some 30 years of surfing and diving, to share the experience of seeing a shark with visitors. To make sure that the predators of the deep will show up for the viewing, Captain Pavsek heaves "chum," a not very appetizing concoction of fish trimmings and entrails, over the side of his 26-foot boat, Kailolo. Sort of like ringing the dinner bell, after a few minutes the sharks (generally gray reef, Galapagos, and sandbars, ranging from 5 ft.-15 ft.) show up -- sometimes just a few, sometimes a couple dozen.

Depending on the sea conditions and the weather, snorkelers can stay in the cage as long as they wish, with the sharks just inches away. The shark cage, connected to the boat with wire line, floats several feet back and a little above the surface, holding two snorkelers comfortably and four snuggly. You can stay on the boat and view the sharks from a more respectable distance for just $60. The brave and adventuresome will be down in that cage, just thin aluminum separating them from jaws. It definitely will be a memory you won't forget.

Snorkeling

Some of the best snorkeling in Oahu is at the underwater park at Hanauma Bay. It's crowded -- sometimes it seems there are more people than fish, but Hanauma has clear, warm, protected waters and an abundance of friendly reef fish -- including Moorish idols, scores of butterflyfish, damselfish, and wrasses. Hanauma Bay has two reefs, an inner and an outer -- the first for novices, the other for experts. The inner reef is calm and shallow (less than 10 ft.); in some places, you can just wade and put your face in the water. Go early: It's packed by 10am and closed on Tuesdays.

Braver snorkelers may want to head to Shark's Cove, on the North Shore just off Kamehameha Highway, between Haleiwa and Pupukea. Sounds risky, we know, but we've never seen or heard of any sharks in this cove, and in summer, this big, lava-edged pool is one of Oahu's best snorkel spots. Waves splash over the natural lava grotto and cascade like waterfalls into the pool full of tropical fish. To the right of the cove are deep-sea caves to explore.

The uninitiated might feel better after a lesson and a snorkel tour. Surf-N-Sea, 62-595 Kamehameha Hwy., Haleiwa (tel. 808/637-9887), has 2-hour tours, with equipment, starting at $45. On the North Shore, Haleiwa Surf Center, 66-167 Haleiwa Rd., Haleiwa (tel. 808/637-5051), teaches snorkeling and offers guided snorkel tours. Aloha Dive Shop, Koko Marina Shopping Center (tel. 808/395-5922), is the closest dive shop to the underwater park at Hanauma Bay.

Sportfishing

Kewalo Basin, located between the Honolulu International Airport and Waikiki, is the main location for charter fishing boats on Oahu. From Waikiki, take Kalakaua Ewa (west) beyond Ala Moana Center; Kewalo Basin is on the left, across from Ward Centre. Look for charter boats all in a row in their slips; on lucky days, the captains display the catch of the day in the afternoon. You can also take TheBus no. 19 or 20 (Airport).

The best way to book a sportfishing charter is through the experts; the best booking desk in the state is Sportfish Hawaii (tel. 877/388-1376 or 808/396-2607; www.sportfishhawaii.com), which not only books boats on Oahu, but on all islands. These fishing vessels have been inspected and must meet rigorous criteria to guarantee that you will have a great time. Prices range from $700 to $817 for a full-day exclusive charter (you, plus five friends, get the entire boat to yourself), $500 to $625 for a half-day exclusive, or from $150 for a full-day share charter (you share the boat with five other people).

Submarine Dives

Here's your chance to play Jules Verne and experience the underwater world from the comfort of a submarine, which will take you on an adventure below the surface in high-tech comfort. The entire trip is narrated as you watch tropical fish and sunken ships just outside the sub; if swimming's not your thing, this is a great way to see Hawaii's spectacular sea life. Shuttle boats to the sub leave from Hilton Hawaiian Village Pier. The cost is $90 to $100 for adults (book on the Internet for just $81-$90), $40 ($35 booked online) for kids 12 and under (children must be at least 36 in. tall). Call Atlantis Submarines (tel. 800/548-6262 or 808/973-9811; www.go-atlantis.com) to reserve. To save money, ask about advance purchase for the shorter "Discovery Adventure," which is only $60 ($50 online) for adults, $40 ($35 online) for children. A word of warning: The ride is safe for everyone, but skip it if you suffer from claustrophobia.

Surfing

In summer, when the water's warm and there's a soft breeze in the air, the south swell comes up -- it's surf season in Waikiki, the best place to learn how to surf on Oahu. For lessons, go early to Aloha Beach Service, next to the Sheraton Moana Surfrider, 2365 Kalakaua Ave., Waikiki (tel. 808/922-3111). The beach boys offer surfing lessons for $25 an hour; board rentals are $8 for 1 hour and $12 for 2 hours. You must know how to swim.

Surfboards are also available for rent at Surf-N-Sea, 62-595 Kamehameha Hwy., Haleiwa (tel. 808/637-9887; www.surfnsea.com), for $5 to $7 an hour. They also offer lessons for $65 for 2 hours.

On the windward side, call Kimo's Surf Hut, 151 Hekili St., across from Daiei, in Kailua (tel. 808/262-1644). Kimo and his wife, Ruth, couldn't be more friendly and helpful. In addition to surfboards ($20 a day) and bodyboards for rent, Kimo has his own personal collection of vintage surfboards, lovingly displayed on the walls of his shop. If you have the time, Kimo will gladly tell you the pedigree and history of each board. Although Kimo doesn't have formal surfing lessons, he'd be happy to give you pointers.

More experienced surfers should drop in on any surf shop around Oahu, or call the Surf News Network Surfline (tel. 808/596-SURF) to get the latest surf conditions. The Cliffs, at the base of Diamond Head, is a good spot for advanced surfers; 4- to 6-foot waves churn here, allowing high-performance surfing.

If you're in Hawaii in winter and want to see the serious surfers catch the really big waves, bring your binoculars and grab a front-row seat on the beach near Kalalua Point. To get here from Waikiki, take the H-1 toward the North Shore, veering off at H-2, which becomes Kamehameha Highway (Hwy. 83). Keep going to the funky surf town of Haleiwa and Waimea Bay; the big waves will be on your left, just past Pupukea Beach Park.

Swimming

For a quiet, peaceful place to swim, Malaekahana Bay, near Kahuku, is one of the best Oahu beaches. This mile-long, white-sand, crescent-shaped beach is about a 90-minute drive and a million miles from the crowds at Waikiki. To get there, take Kamehameha Highway past Laie and follow the signs to Malaekahana State Recreational Area. Or take TheBus no. 52 (Circle Island). Another good swimming beach is Lanikai; secluded and calm, this beach is great for families. From Waikiki, take TheBus no. 56 or 57 (Kailua), and then transfer to the shuttle.

Water-Skiing

To learn to water-ski or to just go out and have a good time, call the oldest water-ski company in Hawaii, Hawaii Sports Wake Board and Water Ski, at Koko Marina Shopping Center (tel. 808/395-3773; www.hisports.com; TheBus: 58). Lessons and boat rental are $69 for a first-time lesson of two 15-minute runs; if you do not need lessons, then prices are $49 for a 20-minute ride and $59 for a 30-minute ride, including the boat and all equipment rental (maximum of five people).

Whale-Watching

From December to April, 45-foot humpback whales -- Hawaii's most impressive visitors -- come to spend the winter. They make the journey from Alaska to calve and mate in Hawaii's calm, warm waters. Once nearly hunted to extinction, humpback whales are now protected by federal law. The mammals may not be approached by any individual or watercraft within 100 yards.

Whales can frequently be seen off the island on calm days. If you spot the familiar spout of water -- a sign the mammal is exhaling -- there's a good chance you'll see the whale on the surface. If you're in a car, please pull over, as many accidents have occurred when visitors try to spot whales and drive at the same time.

Windsurfing

Windward Oahu's Kailua Beach is the home of champion and pioneer windsurfer Robbie Naish; it's also the best place to learn to windsurf. The oldest and most established windsurfing business in Hawaii is Naish Hawaii/Naish Windsurfing Hawaii, 155-A Hamakua Dr., Kailua (tel. 800/767-6068 or 808/262-6068; www.naish.com). The company offers everything: sales, rentals, instruction, repair, and free advice on where to go when the wind and waves are happening. Private lessons start at $55 for one, $75 for two; beginner equipment rental is $25 for a half-day and $30 for a full day. Kite surfing lessons are also available ($100 for 1 1/2 hr.). Kailua Sailboards & Kayaks, 130 Kailua Rd., a block from the Kailua Beach Park (tel. 808/262-2555; www.kailuasailboards.com), offers 3-hour small-group lessons ($49 per person, including all gear) and rentals of windsurfing equipment, surfboards, snorkel gear, and ocean kayaks.

Windsurfer wannabes on the North Shore can contact Surf-N-Sea, 62-595 Kamehameha Hwy., Haleiwa (tel. 808/637-9887; www.surfnsea.com), which offers equipment rental ($12 per hour or $45 for the day), as well as private lessons (beginning at $65 for 2-3 hr.).