Habili Ali

A habili is a reef that never quite grew to the surface, and Habili Ali is the St John's group's strongest expression of the form: a sheer-sided tower standing in open water, its top a few meters down, its base out of sight. With no lagoon or plateau to shelter in, everything happens on the walls and in the current - giant gorgonians on the deeper faces, black coral thickets, grey reef sharks riding the up-current side, and schooling barracuda coiling off the corners. Hammerheads and silvertips pass through in the cooler months, and bumphead parrotfish graze the crest in dawn light. It is a compact, intense dive that punishes sloppy buoyancy and rewards divers who can hold position, look out, and wait.

The moment you come for: Giant gorgonians and black coral; sharks on the up-current face; a pure pinnacle profile with no easy exit.

Topography: A submerged tower rising from deep water to within meters of the surface, walled on all sides

Entry: An exposed St John's pinnacle that never reaches the surface; entries are negative drops onto the up-current face.

Hazards: Strong current with nowhere to hide; blue-water ascents; depth creep on featureless walls.

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