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Without a doubt, Cocos Island is the most famous dive destination in Costa Rica. Located 340 miles/ 550 kilometers off the country's west coast, it is exclusively accessed via liveaboard charter. As a result, trips to Cocos are not cheap—but the wonder of what awaits there makes the expense worthwhile. The island is surrounded by deep oceanic waters punctuated by soaring pinnacles and steep reef walls. This sudden change in topography causes nutrient-rich upwellings, which in turn attract a multitude of pelagic species.
There are around 20 different dive sites at Cocos, and potential sightings range from great schools of gamefish like trevally and tuna; to dolphins, sailfish, turtles and manta rays. Sharks are the main attraction here, however. Regular visitors include Galapagos sharks, bull sharks, tiger sharks, silky sharks and whitetip reef sharks. One of the most famous dive sites, Bajo Alcyone, is known worldwide for its vast schools of scalloped hammerhead. Visibility ranges from 10-30 meters. The best season for wildlife sightings is June to November, when plankton blooms attract the greatest variety of life.
Dive conditions are challenging at Cocos Island, and include deep dives, drift dives and strong current. As a result, this trip is only suitable for experienced Advanced divers.
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Located 10 miles/ 16 kilometers off Costa Rica's southerly Osa Peninsula, Caño Island is part of a biological reserve and famous for its healthy coral reefs. It also boasts beautiful underwater topography, including archways, outcrops and swimthroughs. The visibility is generally good (sometimes exceeding 30 meters), and the abundance of marine life makes this site a worthy alternative for those that don't hive the time or the budget for Cocos.
On any dive, you can expect to see colorful reef fish interspersed with schools of snapper or barracuda, as well as turtles, moray eels and whitetip reef sharks. Occasionally, pelagic visitors make an appearance—think dolphins and larger sharks (and sometimes, migrating humpback and pilot whales). Bajo del Diablo is often considered the area's most rewarding dive site. You can reach Caño Island via day trips from Manuel Antonio or Drake Bay; or you can stay there on a liveaboard charter.
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Off the coast of Costa Rica's northwestern Guanacaste province lies the Catalina Islands, an archipelago of rugged rocky outcrops. Accessible via day trips with dive operators based in Playas del Coco, the islands are famous for giant manta rays. Mantas can be seen there all year round; although the best season for sightings lasts from November until May. Other rays are also present in large numbers, including spotted eagle rays, mobula rays and bullseye round stingrays.
Rays aren't the Catalina Islands's only attraction, however. Experienced divers can also keep an eye out for sharks, turtles and schools of colorful fish. On the way out to the islands, cetacean species including humpbacks and orcas are often spotted. The conditions here usually involve strong currents, so an Advanced certification is advised.
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Also accessible from Playas del Coco, the Bat Islands (or Islas Murcielagos as they're known locally) are another excellent option for divers in the Guanacaste region. You'll need plenty of courage, though, because this is the domain of the mighty bull shark and one of the few places in the world where you can swim with the species outside of a cage. The bull sharks congregate naturally around a site known appropriately as the Big Scare.
Safe diving practices demand a quick descent, and after that, the dive is spent finning along the rocky seafloor in search of sharks. Visibility can vary greatly—as much as 30 meters one day, and as little as five meters the next. The Big Scare is not the only dive site—other highlights include Bajo Negro, a steep pinnacle known for its schooling gamefish and possible manta sightings.