Few sharks are as easily recognizable as the hammerhead, with its tall dorsal fin and wide, scythelike head slicing through the ocean as the muscles ripple down its sleek, gray body. It's a wide-roaming species that can be spotted around the world, but if you're game for the ultimate hammerhead encounter, look to the eastern Pacific, where a trio of locations – Galapagos, Cocos and Malpelo – form what in-the-know divers call the "hammerhead trifecta."

GALAPAGOS
Galapagos Aggressor III

In this volcanic archipelago, liveaboards take you way off the standard nature-watching routes to hammerhead country around the remote seamounts of Wolf and Darwin islands. Hit the water here and descend along the vertical rock face, keeping your head turned to the blue. While big, these sharks are shy — you’ll often spot them swimming endless circles around the seamounts, hanging right on the edge of your visibility. You can swim with the hammers year-round, but December through May offers the best chance to see them schooling in the thousands.

COCOS ISLAND
Okeanos Aggressor
Cocos Wind Dancer

Take a liveaboard from Costa Rica’s Pacific coast to the Cocos Island National Park, and you can dive all day, every day with schooling hammerheads, not to mention a half-dozen other shark species, and gamefish like marlin and tuna. Legendary dive sites like Bajo Alcyone, Dirty Rock and Punta Maria are hammerhead cleaning stations, where you descend to about 100 feet and tuck behind a boulder to escape the ripping currents, and watch the hammerhead show unfold above your head.

MALPELO ISLAND
Undersea Hunter Malpelo Island

This tiny seamount off the coast of Colombia but accessible via Costa Rica is often considered a sister island to Cocos, and many liveaboard trips include both islands. Unlike Cocos, where the hammerhead dives are deep, you can spot huge congregations of these incredible sharks in shallow water — though blistering currents are still the norm. Hammerheads tend to hang above the thermocline, where they sometimes mix with equally large schools of silky sharks, creating superschools of can’t-miss shark action.