10 Amazing Underwater Adventures

Underwater Reef Trail, U.S. Virgin Islands

Under idyllic Trunk Bay's waters off the island of St. John, find a self-guided tour like few others. This 225-yard-long reef trail with posted signage directs snorkelers around a living coral reef replete with tropical fish, stingrays, sea turtles, and other fascinating creatures of the deep and not-so-deep. Beware: Snorkelers are discouraged from touching the reef itself, as it impedes growth and adversely affects local marine life, so keep your fins to yourself. Nearby St. Croix's Buck Island Reef National Monument offers a similar experience.

Cooper River Underwater Trail, South Carolina

South Carolina's wide Cooper River has long been an important commercial waterway, but in its depths lie centuries of history. Embark on the Cooper River Underwater Trail to uncover long-submerged docks and ruins, including the shipwreck at Strawberry Ferry (where four British supply vessels were burned and sunk in 1781 during the height of the American Revolution). Signage directs divers along the two-mile trail (note that the trail is recommended for advanced divers comfortable in low-visibility "dark water").

Atlantis Submarine Tours, Various Destinations

Since 1986, Atlantis Submarines has been plunging passengers into seas around the world, from the shallow reefs of Curacao to the warm waters of Waikiki. The 48- and 64-passenger submersibles are powered by batteries and don't release pollutants into the water—a big draw for ecotourists. Dive to depths of 100 feet or more to explore coral reefs, shipwrecks, sponge gardens, and entire ecosystems of marine life, all without getting even the slightest bit wet.

Jules' Undersea Lodge, Florida

This marine hotel gives "sleeping with the fishes" a whole new meaning. Originally built as a mobile undersea laboratory, Jules' Undersea Lodge in Key Largo, Florida, was refitted to become the world's first underwater hotel. To begin your subaquatic stay, you must scuba dive about five fathoms (30 feet) below the surrounding Emerald Lagoon, a nursery for reef fish. (The lodge's 42-inch windows provide picture-perfect views.) After a day of scuba diving, sink into one of the private bedrooms and order a pizza—the hotel will deliver a pie to your room.

Manatee Snorkel Tour, Florida

What better swimming companion is there than a manatee? Snorkel the Crystal River with Bird's Underwater and explore the manatee's natural habitat. Though these large aquatic mammals weigh, on average, a whopping 1,200 pounds, they are playful and curious with swimmers. Visitors can watch the so-called sea cows graze along the river bottom during a three- to four-hour tour; book during the cooler period from mid-October to mid-March for maximum manatee sightings.

Underwater Sculpture Park, Grenada

We'd never knock conventional museum hopping, but a change of venue is always welcome. British-Guyanese artist Jason de Caires Taylor created this magical museum submerged in Grenada's calm Caribbean waters, where 65 eerily lifelike cement sculptures are anchored to the sea floor. Over time, coral will grow on the pieces, turning them into strange and beautiful living art. Divers can arrange tours of the dynamic sculpture garden through Dive Grenada and other outfits.

Underwater Volcano Dive, Indonesia

Find the aboveground volcano scene a little too "been there, done that"? Dive to the deep end of Indonesia to witness the active volcano Banua Wuhu. A little more than 1,312 feet tall but just feet below the water's surface, Banua Wuhu is completely safe for scuba diving: No lava escapes its vents, and the emitting sulfur gases are harmless. A vibrant marine community of reef sharks and neon tropical fish call its craggy sides home. (Ocean Rover Cruises can get you there.)

Ithaa Undersea Restaurant, Maldives

When you think "underwater activity," the first thing that comes to mind is probably not a six-course meal. The ultraluxe resort Conrad Maldives Rangali Island would like to prove otherwise, with its completely submerged Ithaa Undersea Restaurant. Set more than 49 feet below the surface of the water, Ithaa dishes out stunning under-the-sea views through its transparent acrylic structure. Diners can watch the colorful aquatic life around and above them while they nibble on indulgent fare like caviar and local lobster carpaccio.

Valhalla Missile Silo Dive, Texas

This diving destination isn't just hot—it's positively nuclear. The Valhalla missile silo just outside of Abilene, Texas, ranks as one of the world's largest (and strangest) indoor dive sites. Constructed during the 1960s to house ballistic missiles, the silo was abandoned and became filled with groundwater over time. It's now a unique stop for thrill-seeking scuba divers who plumb the 130-foot water-filled concrete structure and its dark, cold depths; they won't spot any tropical fish here, but there is plenty of scrap metal and Cold War history on view.

Scooter Cruiser Underwater Experience, Mauritius

This is your chance to finally feel like a Bond villain. Whirl around under the sea on the scooter cruiser, a kind of self-propelled mini submarine crossed with a personal scooter. Unlike traditional scuba diving, you don't need a separate breathing tank or mouthpiece; the scooter's massive glass dome encases your head and shoulders and provides a constant air supply. Cruise along a reef northwest of Mauritius at a rate of 2.5 knots (a little less than 3 mph). Other underwater scooter adventures can be found in St. Thomas, Oahu, and Cancun.

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