Roca Partida

Roca Partida is a cleft rock the size of a small building, the visible tip of a seamount standing alone in open ocean - the most concentrated dive in the archipelago because there is nowhere else for anything to be. Whitetip reef sharks lie stacked like cordwood in the wall's few ledges, an image unique to this place. Around the spire, everything rotates: hammerhead schools, silvertips and Galapagos sharks, yellowfin tuna like torpedoes, mantas on their rounds, and in the season's bookends whale sharks. Humpbacks have surfaced beside pangas here. Divers circle the rock, hold in the blue, and try to look every direction at once.

The moment you come for: Whitetips shelved in the ledges, everything-at-once pelagic traffic, the loneliest rock in Mexican waters

Topography: Split guano-white rock spire walls plunging into abyssal water

Current: No lee, no anchorage, no bottom in reach - the dive is a circuit of the rock with the current deciding the route.

Hazards: Full ocean exposure: current, swell, and nothing to hold onto between the rock and the abyss. Strict buddy and DSMB discipline.

Conservation: The long outer leg of the park; weather decides whether boats can stay.

Nitrox: Worth it here: profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).