El Muellito

The shape of the dive is a staircase. You drop onto the reef edge at 7 metres, which is the shelf newly certified divers stay on, and from there the rock falls away in stages: 15 metres, then 19, then 32, before the ground runs on past 40. Where the group turns is decided by its level and its gas rather than by the terrain, because the reef keeps going down whatever the plan says.

Split off from the reef wall, a rock pin stands alone in front of the face and shelters young groupers. It is the one fixed feature on a dive that is otherwise a run along the edge. Large shoals of sardines patrol that edge, and the rock behind them is overgrown with algae and plants and holds a long list of smaller fish. Parrotfish, octopus and cuttlefish are the everyday sightings.

Depth discipline is what the profile asks for. The 32 metre stage and everything under it sits outside Open Water limits, so no-decompression time and gas end the dive rather than the reef. The ascent runs back up the same stages to the 7 metre edge, where the safety stop is held against the top of the reef with the shoals still in sight.