Costa Rica

Costa Rica has two coasts and two entirely different diving propositions.

The Caribbean side — accessed from towns like Puerto Viejo and Limón — is classic warm Caribbean reef diving: warm water, moderate visibility, sea turtles, reef fish, and coral gardens. It's good diving, easy to access, and affordable.

But divers fly to Costa Rica for the Pacific, and for one site above all: Cocos Island.

Coco (Isla del Coco) is a UNESCO World Heritage Site, 36 hours by boat from the Pacific port of Puntarenas, in the middle of where nothing is. It has no permanent inhabitants except a Costa Rican park station. And it has some of the most extraordinary pelagic diving on the planet.

The draw is schooling scalloped hammerheads — hundreds of them on good days, circling the seamounts in the murk, gathering in formations that seem impossible for an animal that supposedly doesn't school. Whale sharks pass through regularly. Silvertip sharks, Galápagos sharks, and whitetip reef sharks are present on virtually every dive. Eagle rays in formations of dozens. Giant manta rays feeding in the surface current.

Cocos is expensive, demanding, and utterly exceptional.

On the mainland Pacific coast, the Bat Islands (Islas Murciélago) in Guanacaste offer bull shark encounters from June through November — large females, resident and accustomed to divers, patrolling shallow reefs at 10–20 meters. The Catalina Islands nearby have clean walls and resident eagle rays and reef sharks.

Best season: June–October for Cocos and the mainland Pacific. December–April for calmer seas, though Cocos runs liveaboards year-round.