Big Island

Exploring Lava Tubes
Strap on a miners hat and gloves and get ready to explore the underbelly of the world's largest active volcano. Tours through these fascinating caves and lava tubes underneath the volcano must be arranged in advance, but are well worth a little extra planning. Located off Highway 11 between Hilo and Volcanoes National Park, the Caverns are comprised of four main tubes, each 500-700 years old and full of stalactites, stalagmites, and a variety of different colored flowstone. The largest lava tube in the world is here -- 40 mi long, it has 80-foot ceilings and is 80 feet wide. Tours can range from safe and easy (safe enough for children five years old and up) to long and adventurous. For those not so sure about "spelunking," an easy walking tour through the lava tube can also be arranged. www.kilaueacavernsoffire.com. Open by appointment only.

Beaching It at Hapuna Beach State Recreation Area
By any measurement, this is one fine beach. Guidebooks usually say it's a toss-up between Hapuna and Kauna'oa for "best beach" on the island, but most locals give the prize to Hapuna. There is ample parking so you don't have to get here at dawn, although it can fill up by midday. And while the north end of the beach fronts the Hapuna Beach Prince Hotel, it's still a public beach and not just for hotel guests. The beach itself is a long ( 1/2-mi), white, perfect crescent, one of the Big Island's largest. The turquoise water is very calm in summer, with just enough rolling waves to make bodysurfing or boogie boarding fun. There's some excellent snorkeling around the jagged rocks that border the beach on either side, but a strong current means it's only for experienced swimmers. In winter, surf can be very rough. Hapuna tends to get a little windy in the late afternoon; even that can have a benefit, as everyone else leaves just in time to give you a private, perfect sunset. There are a couple of small protected coves at the north end of the beach with shallow, sandy-bottomed pools ideal for youngsters.
Address: Hwy. 19, near mile marker 69, at Hapuna Beach Prince Hotel, HI

Kaua’i

Kayaking Napali
In its second year and second issue, National Geographic Adventure ranked kayaking Napali Coast second on its list of "America's Best 100 Adventures," right behind rafting the Colorado River through the Grand Canyon. That pretty much says it all. It's the adventure of a lifetime in one day -- involving eight hours of paddling. Although it's good to have some kayaking experience, feel comfortable on the water, and be reasonably fit, it doesn't require the preparation, stamina, or fortitude of, say, climbing Mt. Everest. Tours run May through September, ocean conditions permitting.

Napali Kayak. A couple of longtime guides for Kayak Kaua'i ventured out on their own a few years back to create this company that focuses solely on sea kayaking -- Na Pali Coast in summer, as the name implies and the South Shore in winter (during peak times only). These guys are highly experienced and still highly enthusiastic about their livelihood. Prices start at $175. You can also rent kayaks; price range from $35 to $70. 5-575 Kuhio Hwy., next to Postcards Café. PHONE: 808/826-6900 or 866/977-6900. www.napalikayak.com

Diving Ni’ihau
For the advanced diver, the island of Ni'ihau -- across an open ocean channel in deep and crystal-clear waters -- beckons and rewards, usually, with some big fish. Seasport Divers and Bubbles Below venture the 17 mi across the channel in summer when the crossing is smoothest. Divers can expect deep dives, walls, and strong currents at Ni'ihau where conditions can change rapidly. To make the long journey worthwhile, three dives and Nitrox are included.

Maui

Ziplining through the Tropics
The latest adventure in Hawaii is "zipping" or "ziplining." It's so new that the vernacular is still catching up with it, but regardless of what you call it, chances are you'll scream like a rock star fan while trying it. Strap on a harness, clip onto a cable running from one side of a river or valley to the other, and zip across. The step off is the scariest part. Pack knee-length shorts or pants, athletic shoes, and courage for this adventure.

Skyline Eco Adventures. First in the United States to offer zipline tours, Skyline Eco Adventures operates in two locations on Maui: the original course on the slope of Haleakala, and the newer venue at 1,000 feet above Kaanapali. Good-natured guides give expert instruction and have you "zipping" confidently across deep gulches and canyons on a narrow zipline. A harness keeps you supported for the quick ride. You must be at least 10 years old, weigh between 80 and 260 pounds, and be able to hike a moderate distance over uneven terrain in order to participate. Closed-toe athletic-type shoes are required, and you can expect to get dirty. For the Haleakala tour ($89), dress in layers, as it can get chilly at the 4,000-plus foot elevation, especially in the morning. The Kaanapali tour ($149) includes breakfast or lunch. Advance reservations are suggested, especially in the summer, and discounts are available for online bookings. Although zipline tours are completely safe, you may want to reconsider this activity if you are uncomfortable with heights or have serious back or joint problems. 808/878-8400. www.zipline.com

Hitting the Beach
Slaughterhouse (Mokuleia) Beach
The island's northernmost beach is part of the Honolua-Mokuleia Marine Life Conservation District. "Slaughterhouse" is the surfers' nickname for what is officially Mokuleia. When the weather permits—usually summer only—this is a great place for bodysurfing and sunbathing. Concrete steps and a green railing help you get down the sheer cliff to the sand. The next bay over, Honolua, has no beach but offers one of the best surf breaks in Hawai'i. Often you can see competitions happening there; look for cars pulled off the road and parked in the pineapple field. No facilities.
Address: Mile marker 32 on Rte. 30 past Kapalua, HI

Kapalua Beach
Kapalua was once named the "world's nicest beach." Walk through the tunnel at the end of Kapalua Place and you'll see why -- the beach fronts a pristine bay good for snorkeling, swimming, and general lazing. Located just north of Napili Bay, this lovely, sheltered shore often remains calm late into the afternoon, although there may be strong currents offshore. This area is quite popular and is bordered by the Kapalua Resort so don't expect to have the beach to yourself. Toilets, showers, parking lot available.
Address: From Rte. 30, turn onto Kapalua Pl., walk through tunnel, HI

O’ahu

Stand Up Paddling
Tried surfing but decided it was too much effort? Well, then, it’s time to try stand up paddling, also called “beach boy paddling.” (Ask a beach boy; he’ll tell you why.) It’s a sport beginners and professionals are taking to like, well, a duck to water. Most surf schools have added stand up paddling lessons to their traditional surfing classes, making it easy to find someone willing to give you a lesson. Even though, we say it’s a sport that’s friendly to all types of beach-goers, we still recommend taking a lesson—definitely.  For a list of surf instructors, click here.

Taking to the Air
The Original Glider Rides. "Mr. Bill" has been offering piloted glider (sailplane) rides over the northwest end of Oahu's North Shore since 1970. These are piloted scenic rides for one or two passengers in sleek, bubble-top, motorless aircraft. You'll get aerial views of mountains, shoreline, coral pools, windsurfing sails, and, in winter, humpback whales. Reservations are recommended; 10-, 15-, 20-, and 30-minute flights leave every 20 minutes daily 10-5. The charge for one passenger is $59-$139, depending on the length of the flight; two people fly for $138-$238. Dillingham Airfield, Mokuleia. 808/677-3404