Brian J. Skerry / National Geographic / Getty Images
Santa Rosalia, Sea of Cortez, Mexico
Where It Is: On the western edge of the Sea of Cortez, halfway down the Baja Peninsula, the town of Santa Rosalia is known as a base for divers in search of one of the ocean’s nastiest predators.
What to Look for: The Humboldt squid, which can grow to six feet in length, has tentacles lined with teeth and a beak that can shred fish in an instant. The predatory squids—whose pale, waxy arms, elongated heads, and rows of powerful suckers make them resemble space aliens—frequent the deep waters in large groups and come up to feed. Though they live in the Pacific Ocean from South America to California, sightings in this part of the Sea of Cortez are so common that Mexican fishermen have a special name for them: Diablos Rojos (“Red Devils”).
Channel Islands, California
Where It Is: Sometimes called “the North American Galapagos,” this chain of eight islands lies 150 miles off the coast of southern California, roughly between San Diego and Santa Barbara.
What to Look for: A confluence of cold northern water and warm southern currents makes for an extraordinary spectrum of sea life here. Giant kelp forests, with stalks that rise more than 100 feet from the sea floor, shelter species ranging from sea lions and great white sharks to cartoonish Garibaldi fish and crayon-bright Hermissenda crassicornis sea slugs.
Bikini Atoll, Marshall Islands
Where It Is: Infamous as a nuclear-weapons testing ground in the 1940s and 1950s, this string of three dozen small islands surrounds a lagoon near the intersection of the equator and the international dateline.
What to Look for: Bikini Atoll is one of the world’s top spots for wreck diving. Now that radiation levels have fallen to safe levels, deep-water divers can descend some 100 feet into the lagoon—now a ship graveyard—and swim among dozens of sunken vessels, including wrecked World War II naval ships. Many still have preserved guns and other ordnance that are easily visible in the clear water. Steve Mortell, a training supervisor with the Professional Association of Diving Instructors, said that at the Bikini Atoll dive center, “you can watch actual WWII films of the wrecks you are going to dive on the next day.”
Ken Knezick — Island Dreams
Wakatobi Archipelago, Indonesia
Where It Is: Set in the Indonesian province of South East Sulawesi, the Wakatobi preserve spreads across hundreds of square miles of thriving coral reefs, which surround an archipelago of four main islands.
What to Look for: Due to its remote and untouched setting, Wakatobi has some of the broadest biodiversity in the entire Pacific Ocean. Divers often see reef sharks, pilot whales, mobula rays, black blotched stingrays, barracudas, humphead parrotfish, and even the occasional orca. The coral outcroppings are also home to invertebrates like ghost pipefish, bobtail squid, Napoleon snake eel, warty frogfish, and many other obscure species.
Fathom Five National Marine Park, Ontario
Where It Is: Lake Huron’s icy waters preserve sunken ships for decades with little disturbance. Fathom Five Marine Park, a land and water reserve on Lake Huron’s Georgian Bay at the end of the Bruce Peninsula, is a four-hour drive north of Toronto.
What to Look for: With 22 significant shipwrecks dating back to the 19th century, Fathom Five presents a microcosm of maritime history. The wrecks include shallow-water hulks that even snorkelers can enjoy, but also wood-hulled schooners more than a dozen fathoms deep. Among the latter is the Arabia, a schooner that sank in 1884; according to Dan Orr, the CEO of Divers Alert Network, the ship’s bowsprit “points a lonely finger towards the surface nearly 100 feet above.”
Ras Mohammed National Park, Egypt
Where It Is: Where the parched landscapes of Egypt’s Sinai Peninsula surrender to the Red Sea, Ras Mohammed National Park splays out as an arid preserve with cliffs, sand dunes, beaches, inlets, and—for divers—unique underwater topography.
What to Look for: Dramatic rock overhangs, sheer underwater cliffs, and deep gullies define several dive sites at Ras Mohammed, where schools of barracuda and hammerhead sharks are among the varied sea life. Particular dive sites here, like Shark Reef and Yolanda Reef, feature innumerable starfish, sea urchins, mollusks, and crustaceans. Farther offshore, the ghost hull of the Thistlegorm, a British Merchant Navy ship that sank in 1941, is a well-known wreck dive.
Raja Ampat, Indonesia
Where It Is: Four large islands and hundreds of smaller land masses make up the immense archipelago of Raja Ampat, set in the Pacific waters off the Bird’s Head Peninsula of eastern Indonesia. There are hundreds of dive sites among these islands.
What to Look for: The marine life diversity here is some of the richest in the world, with hundreds of species of coral supporting an enormous spectrum of sea creatures. Pygmy sea horses, walking sharks, unicorn fish, and manta rays with 10-foot wingspans are all frequently sighted here. World War II–era shipwrecks, including a Japanese naval patrol vessel, add to Raja Ampat’s intrigue.
Utila Island, Honduras
Where It Is: Off the coast of Honduras and at the southern end of the Mesoamerican Barrier Reef System—a series of reefs stretching some 450 miles across the Caribbean Sea—Utila is a 12-square-mile island surrounded by world-class dive spots.
What to Look for: The main attraction here—in spring and fall—is the whale shark, the largest fish species on earth. Though these creatures can be 30 feet long and weigh up to 20 tons, they’re safe for divers to swim among (they feed only on plankton and other tiny sea creatures). It’s pretty spectacular to get close to a whale shark, or even to see one in the distance, floating through the warm sea like an underwater zeppelin.
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Los Islotes, La Paz, Mexico
Where It Is: At the northern end of the Espiritu Santos islands, a group of islands dotting the waters in the Bay of La Paz, Los Islotes is a pair of craggy islets home to a large colony of California sea lions. The Espiritu Santos Islands is a National Marine Park in the Sea of Cortez.
What to Look for: The main scuba objective at Los Islotes is a swim with the resident sea lions, which bark, lounge, and dwell in a gap between the rocky islets. The animals are accustomed enough to the presence of divers, says Luke Inman, a professional underwater cinematographer who regularly dives there, that they’ve become “almost domesticated.” Swimming among the playful and curious lions, Inman says, is “akin to jumping into a big bucket of Labrador puppies.”