Aruba offers enough coral reefs, marine life, and wreck diving to keep scuba divers and snorkelers busy for days. The coastal waters have an average temperature of 80°F (27°C), and visibility ranges from 18 to 30m (59-98 ft.). Snorkelers: Be forewarned that waves can be choppy at times in some locations. Divers should wear wet suits, especially for deeper dives (the water doesn't always feel like 80°F). The best snorkeling sites are around Malmok Beach and Boca Catalina, where the water is calm and shallow, and marine life is plentiful. Dive sites stretch along the entire southern, leeward coast. Whatever you do, don't miss a visit to the Antilla wreck, the best shipwreck in the Caribbean. The easiest dive wreck you'll ever see, its mast is so close to the surface that curious pelicans actually used it as a perch up until January 2009, when the wreck shifted.

Besides snorkeling, SNUBA is another nonscuba underwater option. SNUBA divers breathe compressed air through a regulator on a hose attached to a tank floating at the surface. Though entertaining, interference with the line, guide, other SNUBA divers attached to the same tank, and unintended encounters with the razor-sharp reef make the experience at times frustrating and potentially painful.

Diving Do's: Hands Off the Fish! -- While all major dive certification groups do a fantastic job of training divers in all aspects of safety and responsible diving, they are unable to track graduates to make sure they practice what they learned. Even dive masters and dive instructors, who undergo extensive and rigorous training, sometimes forget the lessons they are trained to convey to students. I observed a prime example of forgetting to practice what you preach while diving in Curaçao. A 60-year-old PADI dive instructor brought a cohort of students to the Caribbean, and petted a moray eel in front of the group while having his picture taken. When I later asked him about how he could violate the most fundamental safety rule for both divers and the delicate marine creatures, his response was that he'd done no harm because he was wearing diving gloves. This seemingly harmless act put both the diver and the eel in danger: Diving gloves certainly would not protect the diver from a toothy chomp from a 1.5m (5-ft.) eel, and the touch subjected the eel to acute stress and possible skin infection. None of the above could compare, however, to the standard of deplorable conduct he conveyed to his disciples, who may venture forth to chase, grab, pet, stroke, and otherwise disturb countless other creatures, and set equally bad examples for other divers.

The Operators

Unique Sports of Aruba (tel. 297/5-UNIQUE [586-4783] or 586-0096; www.uniquesportsaruba.com), on Palm Beach at the Radisson, is another popular operation that took over Pelican Adventures dive operations in 2008. Its four boats can accommodate 25 divers comfortably. Packages start at $125 for three dives (assuming you have your own equipment), $320 for six, including equipment. The full-service, five-star, PADI-certified Gold Palm operator has an array of diving options. Two-tank morning boat dives are $81, one-tank morning or afternoon boat dives are $54, and one-tank night dives are $63. Nondiving boat passengers pay $25, or $30 to snorkel, space permitting. Snorkeling cruises include instructions, equipment, stops at three sites, snacks, and an open bar for $45. Pelican (tel. 297/587-2302; www.pelican-aruba.com) also conducts 1-day introductory scuba courses ($96) and full-fledged PADI open-water certification instructions ($438).

Red Sail Sports  (tel. 297/586-1603; www.redsailaruba.com), another full-service, five-star, PADI-certified Gold Palm operator, has locations at the Hyatt, Marriott, and Renaissance. Its dive prices are slightly lower than Unique Sports': Two-tank morning boat dives are $79, one-tank morning or afternoon boat dives are $49, and one-tank night dives are $55. Packages include a 5-tank package for $188, an 8-tank package for $285, and a 10-tank package for $356 excluding gear. Nondiving boat passengers pay $20, space permitting. Snorkelers are charged $30, including equipment, but Unique Sports, Pelican, Red Sail, and other operators offer an array of snorkeling-only excursions that visit multiple sites. Red Sail also offers 1-day introductory scuba and refresher courses that include instructions, a morning pool session, a one-tank boat dive, and all equipment for $99. The PADI open-water certification course is $425 or you can do the classroom portion online and bring the price down to $325. Introductory courses are available for children 10 and over.

Two other dive schools operate in the resort area. S.E. Aruba Fly 'n Dive (tel. 297/588-1150; www.se-aruba.com) operates out of Oranjestad harbor and Surfside Beach. It specializes in dives along the island's southeast coast. As the only PADI five-star National Geographic Center on the island, they offer all courses from beginner to instructor. Mermaid Sports Divers (tel. 297/587-4103 or 587-4106; www.scubadivers-aruba.com) is located between the Low-Rise and the High-Rise hotels on the Sasaki Highway and offers a free dive to anyone who spots a sea horse.

Diving: Taking the Plunge -- If you weren't born with gills, you'll have to learn certain skills and gain an understanding of your equipment before you scuba dive. Contact the Professional Association of Diving Instructors (PADI), the National Association of Underwater Instructors (NAUI), or Scuba Schools International (SSI) for instruction. Certifying 70% of U.S. divers and 55% of divers worldwide, PADI, 30151 Tomas St., Rancho Santa Margarita, CA 92688 (tel. 800/729-7234; www.padi.com), is the world's largest diving organization. Equally respected but less of a marketing powerhouse, NAUI, 1232 Tech Blvd., Tampa, FL 33619 (tel. 800/553-6284; www.nauiww.org), is a not-for-profit association that's been around for 40 years. The last of the big three is SSI, 2619 Canton Court, Ft. Collins, CO 80525 (tel. 970/482-0883; www.divessi.com), which certifies its divers exclusively through retail dive shops.

The Sites

At the island's extreme northeast point, the California wreck has haunted the ocean floor for almost 100 years. While traveling from Liverpool to Central America, the wooden passenger ship ran aground, its merchandise, clothing, and furniture eventually washing ashore. Tour guides often circulate the romantic notion that the ship was the only vessel to have heard the Titanic's distress signal. It's a nice story but a bunch of malarkey. The ship that ignored the Titanic's flares was the Californian, which was torpedoed by a German submarine off the coast of Greece in 1915. About 14m (46 ft.) beneath the ocean's surface, what's left of Aruba's California is difficult to see and rarely visited by dive boats. Due to strong currents and choppy seas, this dive is strictly for advanced divers, and only when the water is unusually calm.

At Arashi Reef, around the island's northern tip from the California, pieces of a Lockheed Lodestar litter the silty bottom of tranquil Arashi Bay. The wings, cockpit, and front half of the fuselage sit upright in a frozen takeoff position. Maybe the neighborhood angelfish, parrotfish, sergeant majors, yellowtail snappers, Caesar grunts, gray chromis, and blue tangs are contemplating how to reassemble all the pieces. Just south of the plane parts, brain coral, star coral, and sea rods dot the strip before dropping off to a ledge painted with sea fans and multicolored encrusting sponges. The plane's depth of 11 to 12m (36-39 ft.) is ideal for novice divers and snorkelers.

Just south of Arashi Reef, the 394-foot-long Antilla wreck is the Caribbean's largest shipwreck, and the only one you can easily experience as a snorkeler. Once a German freighter, the ship was scuttled in 1941 when threatened by Allied forces. In January 2009 part of the hull caved in due to strong currents, and the crow's nest, which once jutted from the water, is now submerged. Even so, its proximity to the surface means even snorkelers can peer into the abyss of its fractured hull and imagine (or try not to) what creatures of the depths may lurk within. It's one of the island's most popular dives. Covered by giant tube sponges and coral formations, the 18m-deep (59-ft.) ghost ship draws angelfish, silversides, moray eels, and the occasional lobster. Octopus, sergeant majors, and puffers can also be spotted.

Leaf and brain coral await you at Malmok Reef, just south of the Antilla. This 21m-deep (69-ft.) bottom reef's dozing lobsters and stingrays are popular with underwater paparazzi, and the giant purple, orange, and green barrel sponges pose for the camera as well. The Debbie II, a 118-foot fuel barge sunk in 1992, attracts schools of fish, including barracuda.

Southwest of Malmok Reef, the mangled midsection is all that remains of the Pedernales, an American flat-bottomed oil tanker torpedoed by a German submarine in 1942. Cabins, washbasins, lavatories, toilets, and pipelines are scattered about for easy viewing. The bow and stern were hauled back to the United States, refitted with a new hull, and used to transport troops for the Normandy invasion. Chunks of the hull, supports, and crossbeams litter the sandy bottom. The wreckage attracts Caesar grunts, green moray eels, frogfish, trumpet fish, groupers, parrotfish, angelfish, silversides, and yellowtail snappers. Keep an eye open for snake eels and spotted eagle rays, too. White tunicates and orange cup corals coat the metal undersides. At a depth of only 6 to 9m (20-30 ft.), the Pedernales is popular with novice divers and snorkelers.

Off the coast of Oranjestad, Harbor Reef features an abundance of hard and soft coral formations, including giant brain coral and orange, black, and blue sponges. Nearby, the aging pilot boat wreck is encrusted with sponges and brain, star, and sheet coral. The queen angels, parrotfish, and Spanish hogfish bathe the 36-foot vessel in fiesta colors, while a barracuda and a pair of green morays keep divers alert. You may also spot the occasional stingray or spotted eagle ray.

An artificial reef 46m (151 ft.) from Renaissance Island's main beach is being helped along by a vintage 1970s Aruba Airlines passenger jet that was sunk 26m (85 ft.) down. The plane sits in takeoff position; the airline logo on the outer hull is still legible. In only 4m (13 ft.) of water and a bit farther off Renaissance Island's main beach, a sunken barge with crowds of swarming fish is also perfect for snorkeling.

Nearby, Sponge Reef is the home of a remarkable array of sponges, including orange elephant ears, purple and yellow tubes, vases, and small baskets. Interesting leaf and plate coral formations are also found in the area.

Farther east but still only 6.4km (4 miles) southwest of Oranjestad, Barcadera Reef stretches from depths of 6 to 27m (20-89 ft.), accommodating both divers and snorkelers. Dense clusters of elkhorn, staghorn, and finger corals populate the reef, and along the sandy bottom, brain corals and huge sea fans hold sway. Wrasses, scorpionfish, blue and stoplight parrotfish, damselfish, and pink-tipped anemones also set up housekeeping in the area.

West of Barcadera Reef at a depth of 27m (89 ft.), the Jane Sea wreck rests in a thick grove of star, boulder, plate, and brain coral. This 246-foot Venezuelan cement freighter was sunk in 1988 to form an artificial reef after it was caught with a cargo of cocaine. Blanketed with hydroids, fire coral, and encrusting sponge, the anchor chain is completely rigid. The ship's sides are orange with cup corals and home to French and queen angels. Keep your eyes peeled for barracuda, green morays, tropicals, and gorgonians, and watch your head when entering the radio room and mess hall.

Even before snorkelers leave the dock of De Palm Island (east of the Jane Sea wreck), overfed fluorescent blue parrotfish looking for a snack greet them. Though it's tempting to feed them, don't do it. Their powerful beaks and digestive tracts are designed to munch on rock-hard corals, and if they eat what people feel them instead of the coral, it is unhealthy for both the fish and the reef -- not to mention somewhat risky for your delicate fingers. Water depths start at 1.2m (4 ft.) at the dock but drop off to 36m (118 ft.) by the time you're 364m (1,194 ft.) out. Divers, who usually reach the reef by boat, are likely to spot a barracuda or two, but snorkelers, who will be underwhelmed by the fish found milling about the damaged reef boulders, will find better diversity elsewhere.

Off the central coast of De Palm Island, Mike's Reef offers one of Aruba's best reef dives. Enormous clusters of gorgonians, brain coral, flower coral, and star coral dominate the environment, while brilliant purple and orange sponges direct the procession of rainbow runners and barracuda. This reef is especially popular with macro photographers (underwater photographers who specialize in close-up shots).

Just east of Mike's Reef and 110m (361 ft.) out from Mangel Halto Beach, Mangel Halto Reef slopes from 4.5m (15 ft.) to ledges and ridges that plunge to depths of 33m (108 ft.). The area boasts an array of deepwater gorgonians, anemones, and sponges. Mobile marine life includes copper sweepers, grunts, sergeant majors, lobsters, blue tangs, butterfly fish, stingrays, yellow tails, and jacks. You may even spot a sea horse. At the greater depths, octopuses, green morays, nurse sharks, tarpons, and large barracuda inhabit small caves and overhangs. In early spring, graceful sea turtles appear on their way to lay eggs on the nearby beaches.

Continuing east along the coast, Isla de Oro Reef rests off the old fishing village of Savaneta. Close to the mangrove-lined shore, the reef is usually swept by a running current, and visibility is excellent. Beginning at 6m (20 ft.), yellow stingrays, lobster, and Spanish hogfish dart along the walls of staghorn, star, brain, and plate corals. Toward the ultimate depth of 36m (118 ft.), sheet and leaf corals form ledges and caves -- home to large morays and parrotfish.

A bit farther east, Commandeurs Reef slopes from 12 to 27m (39-89 ft.) below the surface. Sheet and leaf coral here attract extensive marine life such as snappers, grunts, and French and queen angels. On occasion, runners and barracuda patrol the area.

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.