This is why you've come to Maui -- the sun, the sand, and the surf; about the best beaches, from where to soak up the rays to where to plunge beneath the waves.

Activity Warehouse (tel. 800/343-2087; www.travelhawaii.com), which has branches in Lahaina at 578 Front St., near Prison Street (tel. 808/667-4000), and in Kihei at Azeka Place II, on the mountain side of Kihei Road near Lipoa Street (tel. 808/875-4000), rents everything from beach chairs and coolers to kayaks, boogie boards, and surfboards.

Snorkel Bob's (www.snorkelbob.com) has snorkel gear, boogie boards, and other ocean toys at four locations: 1217 Front St., Lahaina (tel. 808/661-4421); Napili Village, 5425-C Lower Honoapiilani Hwy., Napili (tel. 808/669-9603); in North Kihei at Azeka Place II, 1279 S. Kihei Rd. #310 (tel. 808/875-6188); and in South Kihei/Wailea at the Kamaole Beach Center, 2411 S. Kihei Rd., Kihei (tel. 808/879-7449). All locations are open daily from 8am to 5pm. If you're island hopping, you can rent from a Snorkel Bob's location on one island and return it at a branch on another.

Every winter pods of Pacific humpback whales make the 3,000-mile swim from the chilly waters of Alaska to bask in Maui's summery shallows, fluking, spy hopping, spouting, and having an all-around swell time.

The humpback is the star of the annual whale-watching season, which usually begins in December or January and lasts until April or sometimes May. About 1,500 to 3,000 humpback whales appear in Hawaii waters each year. Adults grow to be about 45 feet long and weigh a hefty 40 tons. Humpbacks are officially an endangered species: In 1997 some of the waters around the state were designated the Hawaiian Islands Humpback Whale National Marine Sanctuary, the country's only federal single-species sanctuary.

Whale-Watching From Shore-- Between mid-December and April, you can just look out to sea. There's no best time of day for whale-watching, but the whales seem to appear when the sea is glassy and the wind calm. Once you see one, keep watching in the same vicinity -- they might stay down for 20 minutes. Bring a book -- and binoculars, if you can.

Everyone dives Molokini, a marine-life park and one of Hawaii's top dive spots. This crescent-shaped crater has three tiers of diving: a 35-foot plateau inside the crater basin (used by beginning divers and snorkelers), a wall sloping to 70 feet just beyond the inside plateau, and a sheer wall on the outside and backside of the crater that plunges 350 feet. This underwater park is very popular thanks to calm, clear, protected waters and an abundance of marine life, from manta rays to clouds of yellow butterfly fish.

Ed Robinson's Diving Adventures (tel. 800/635-1273 or 808/879-3584; www.mauiscuba.com) is the only Maui company rated one of Scuba Diver magazine's top five best dive operators for 7 years straight. Ed, a widely published underwater photographer, offers specialized charters for small groups. Two-tank dives are $120 ($135 with equipment); his dive boats depart from Kihei Boat Ramp.

To really appreciate Maui, you need to get off the land and get on the sea. Trade winds off the Lahaina Coast and the strong wind that rips through Maui's isthmus make sailing around the island exciting. Many different boats, from a three-masted schooner to spacious trimarans, offer day cruises from Maui.

Day Cruises to Molokai
You can travel across the seas by ferry from Maui's Lahaina Harbor to Molokai's Kaunakakai Wharf on the Molokai Princess (tel. 800/275-6969 or 808/667-6165; www.mauiprincess.com). The 100-foot yacht, certified for 149 passengers, is fitted with the latest generation of gyroscopic stabilizers, making the ride smoother. The ferry makes the 90-minute journey from Lahaina to Kaunakakai daily; the cost is $85 for adults and $43 for children (ages 3-12) round-trip. Or you can choose to tour the island from two different package options: Cruise-Drive, which includes round-trip passage and a rental car for $169 for the driver, $80 per additional adult passenger, and $40 for children; or the Alii Tour, which is a guided tour in an air-conditioned van plus lunch for $169 for adults and $109 for children.