If you loved Captain Nemo and 20,000 Leagues Under the Sea, don't miss your chance to cruise 45m (148 ft.) below the sea in a submarine. Atlantis Adventures (tel. 297/588-6881; www.atlantisadventures.com) operates a spacious, modern ship with large portholes for maximum ogling. After a comprehensive orientation on shore, you board a catamaran for the 30-minute sail to deeper water, then transfer to the Atlantis VI, a 66-foot-long, fully pressurized and air-conditioned submarine. During the gentle descent, you'll pass scuba divers, coral reefs, shipwrecks, and hundreds of curious sergeant majors, blue chromis, creole wrasse, parrotfish, and angelfish. Brain and sheet coral, sea whips, and tube and barrel sponges are just as easy to spot during the 50 minutes you're submerged. The crew's commentary is expert, informative, and very wry. Trips depart two to three times each day, at 11am, noon and 1pm.. Each excursion takes 1 3/4 hours, though you are only underwater for 50 minutes. The cost is $105 for adults, and $79 for children 12 and under. All passengers must be at least 91 centimeters (36 in.) tall. It's worth the splurge, but for a cheaper option consider Atlantis's other ship, the Seaworld Explorer. This glass-bottom semisubmarine remains above sea level, but its observatory is 1.5m (5 ft.) below the surface. The narrated tour covers Arashi Reef and features an up-close encounter with a scuttled World War II German freighter, encrusted with coral and teeming with other marine life. The daily voyages are $44 for adults, $24 for children 11 and under, and gratis for toddlers 1 and under. The Atlantis VI trip leaves from a pier in front of the Crystal Casino in Oranjestad; the Seaworld Explorer excursion departs from Pelican Pier on Palm Beach.

If you don't mind getting a little wet but have no desire to learn to scuba dive, consider the Sea Trek helmet dive offered by De Palm Tours (tel. 297/582-4400; www.depalm.com). Donning a wet suit and a Teletubbies-inspired helmet that supplies a continuous flow of air, you'll descend 6m (20 ft.) beneath the sea to a 105m (344-ft.) walkway, where you can feed the fish, view a sunken Cessna, and generally experience life underwater. If you can walk and breathe, don't deprive yourself of the fun. The 40- to 45-minute stroll is $55 plus the $79 cost of passage to the island. A word to the wise: Although Sea Trek and other fun activities are on De Palm Island, don't let anyone convince you to spend all day there. Its beaches are rocky and generally dismal compared to those of the main island, and the snorkeling is unimpressive except for those enormous overfed blue parrotfish.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.