FOR MANY visitors, Hawaii is synonomous with Honolulu's commercial strip, Waikiki Beach, and a mai-tai by the pool. If they're feeling really adventurous, they may rent a car and make the four-hour drive around the island of Oahu, where Honolulu is located. But many more tourists are content to just tune into the video tour on the "Alohavision" closed-circuit channel of their hotel roo, TV set.

About half of the four million travelers who visit here annually see a glimpse of Hawaii that isn't much different from the one they get watching reruns of "Hawaii Five-O." They never leave Oahu, even though the Neighbor Islands, as the natives refer to Maui, Kauai, Hawaii and Molokai, are easily accessible in terms of both cost and distance by commuter airlines. A flight from one end of the archipelago to the other takes just 90 minutes, although you should allow at least a half day to make any interisland tour worthwhile.

The Neighbor Islands reflect a different side of Hawaii. Here, density has to do with the overgrowth of jungle vines, and the saffron beaches are footprint-free. A detour off the beaten path can lead to exploring undersea caves and the colorful denizens of a coral reef, or soaring 3,000 feet above ground on the trade winds.

On the Big Island, Hawaii, adventure can mean hunting wild boar and turkey on horseback..On Kauai, it can mean backpacking through the 4,000-foot-deep Waimea Canyon, known as the Grand Canyon of the Pacific, and navigating the surf-sculpted caverns along the Na Pali coast by rubber boat.

You won't find this side of the Hawaiian Islands on the Gray Line bus tour. But you don't need to know a lifelong resident to find adventure in Hawaii, either. In most cases, all you need do is phone the local office of the Hawaiian Visitors Bureau or a local travel agent's office.

Skimming across the ocean in a motor-driven rubber raft along Kauai's craggy northern 14-mile coast is typical of the kind of easily accessible side trip adventure that awaits the visitor. Na Pali State Park is just a 15-minute drive from one of the most luxurious and largest resort developments on the island, Princeville. Yet this cliff-lined shoreline is Hawaii without high-rise hotels or paved roads--in fact, there are no roads at all. The only ways to enter the state park are on foot or by boat. It is as unspoiled today as it was when Capt. James Cook first set foot on Kauai in 1778.

These days, however, it's Captain Zodiac who plies the furrowed coast. Captain Zodiac is the moniker Clancy Greff borrowed from his fleet of five sleek black inflated-rubber craft known as Zodiacs. These French-made, engine-powered 16- to 20-foot rafts, which were designed by Jacques Cousteau, are the ideal vehicles for riding the ocean swells, navigating the sea caves and landing on the pristine beaches.

Because the craft is flexible, you don't have that pounding feeling in the surf--it's more like a roller coaster ride. It's exciting because you're only sitting one foot above the water.

And Greff seems the ideal guide. An enterprising ex-surf bum, he parlayed his ocean experience and natural interest in folklore into a thriving tour business, Na Pali Zodiac. He knows the ancient Hawaiian legends associated with this broodingly mystical place and the Hollywood legends in the making--the numerous films shot on location here, which include "Raiders of the Lost Ark" and the final scene from "Body Heat."

Greff and his guides also know every nook, cranny and isolated beach nature has tucked into the furrows and caverns that consititute the Na Pali coast. Although rough surf makes maneuvering inside the caves too dangerous during the winter, side trips into great caverns like Pirate's Cave, the Cave of Terror and Circle Cave are a regular feature of summer expeditions.

Landings along the coast are strictly controlled by the local park authority to prevent armadas of tour boats from converging on the beaches. Two other firms, Kauai Zodiac and Na Pali Coast Boat Charters, also serve the Na Pali coast. But for now, Na Pali Zodiac's captains are the only ones permitted to land at designated beaches in the state park area.

Na Pali Zodiac's regular service (weather conditions permitting) includes two types of tours--the 5 1/2-hour round trip from the home port of Hanalei Bay with a picnic stop (bring your own lunch and drinks) on a remote beach ($70 per person) and three-hour morning and sunset cruises ($40 per person). Beach drops for backpackers ($40 each way) depart twice a day. In addition, hauling of camping equipment, private charters and snorkeling excursions can also be arranged. Reservations should be made well in advance, particularly during the popular summer months. (P.O. Box 456, Hanalei, Hawaii 96714; 808-826-9371.)

About an hour's drive from downtown Honolulu lies probably the best-kept secret among Hawaii's natural wonders and one of the island's most exciting side-trip adventures. Here, along the northwest shore of Oahu, the trade winds blow perpendicular to the coastal Waianae Mountains, creating updrafts that make for perfect glider flying conditions. The U.S. government has contributed a 9,000-foot runway, that of Dillingham Airfield, an old World War II fighter base. And Bill Star, a commercial pilot who migrated from California, had the good sense to help establish the Honolulu Soaring Society at this spot. He operates Hawaii's only glider-for-hire business out of the back of his station wagon at the end of the airstrip.

With experienced commercial pilots at the controls of the tow plane and the glider, you just sit back and enjoy 30 minutes of soaring silently thousands of feet above the coastline, without the distractions of vibrating engines.

"Conditions here are ideal," Star says. "Most people who fly sail planes consider five hours an extraordinary flight. But here you can stay up all day long."

The ride of a glider is surprisingly smooth and stable--not at all the white-knuckle experience some expect, but one similar to riding in a small engine plane--without the noise. The thrill comes from the breathtaking bird's-eye view and the feeling that you're in perfect harmony with the elements. If you've seen the movie "To Fly" you'll understand. From up there, the mountains appear to be carpeted with green velvet and the shoreline shimmers like aqua satin fringed with lacy white foam.

One- and two-passenger sail planes lift off daily from Dillingham Field between 10 a.m. and 5:30 p.m. (808-623-6711). No reservations are needed, but you may have to wait 30 minutes for your turn. The fare is $29 for one passenger, $39 for two.

If you're ready to make the jump from occasional, impromptu adventures to three-day or more expeditions, then Sea Trek Hawaii is the way to go. This nonprofit foundation, which was developed as a summer credit course for University of Hawaii instructors, specializes in unique outdoor recreational and educational programs designed to show you the Hawaii few tourists ever see.

Typically, an expedition may include hiking a winding wilderness trail into a volcanic moonscape, exploring an ancient Hawaiian temple(heiau), or snorkeling off one of the many coral reefs teeming with tropical fish. For oceangoing, interisland expeditions, a 38-foot sloop called the Paragon comfortably accommodates a crew of two, a trek leader and six passengers.

The back-to-nature philosophy that underlies Sea Trek's approach doesn't necessarily mean roughing it, however. The Paragon is outfitted with such amenities as an enclosed head, kerosene stove and well-stocked refrigerator, and dinners featuring the fresh catches of the day are standard expedition fare. The guides, or trek leaders, are all instructors from the University of Hawaii. They are as skilled at weaving the natural history of the islands, the people and their culture into each outing as they are at instructing you in safely negotiating the reefs and ravines.

Sea Trek Hawaii (P.O. Box 1585, Kaneohe, Hawaii 96744; 808-235-6614) offers nine different excursion packages. The shortest trek ($320 per person) is a three-day sail from Lanai to Oahu, which includes snorkeling along Lanai's secluded coastal areas, some of the most scenic underwater spots in the islands.

The longest trek ($1,250 per person) is an 18-day combination sailing, camping and hiking expedition that includes five islands--Kauai (point of origin), Hawaii, Maui, Lanai and Oahu (final destination). Trekkers hike through Kauai's canyons, view a sunrise from 10,000 feet atop Maui's Haleakala crater--known as the House of the Sun--and explore the coast of Lanai from below and aboard a 65-foot catamaran. The high point of the trip is a simple but authentic luau prepared in the home of a Hawaiian family.

Meals and transportation, except where interisland flights are not part of the expedition, are included in the prices of all Sea Trek packages.