El Bajo Seamount

El Bajo is a piece of diving history that still earns its place honestly. In the 1970s and 80s this seamount northeast of Los Islotes made the Sea of Cortez famous as the place to swim with schooling hammerheads; overfishing in the wider gulf has since thinned those schools drastically, and today a hammerhead here is an event rather than an expectation - a decline worth stating plainly. What remains is a strong open-water dive: mobula squadrons pulsing over the ridges, big amberjack and tuna hunting through, green morays in the rocks, dolphins on the crossing, and the occasional whale shark cruising past on migration. Old glory, current honesty, still worth the fuel.

The moment you come for: Mobula flights over the ridges, pelagic traffic, the gulf's most storied seamount

Topography: Three rocky ridges rising from deep water to about 18 m

Current: An open-water bank; current and chop decide whether boats make the run.

Hazards: Open-water exposure, current over the ridges, depth accumulating quickly off the crowns.

Conservation: The hammerhead decline here is one of the gulf's cautionary tales; report sightings to your operator - local monitoring uses them.

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