Santa Rosa Wall

The boat drops you at the south end over sand, about eighteen metres down, and the guide puts the group on the edge of the wall. After that you mostly stop swimming. The current sets north along this coast and carries the whole dive one way, to a pickup further up the reef line.

The ground under you is not a single face. It stands in coral columns with sand running between them, so the first stretch crosses a run of shallow canyons draining seaward, and where those end the wall goes vertical and keeps going down. Beside it the reef crest is cut through by crevices, overhangs and short tunnels, and a passage takes you off the wall and puts you out on the sand, or the reverse. Some are wide enough for two divers side by side, others are single file, and which ones the group takes is the guide's call, made in the water.

The overhangs are also where you get out of the current, and they are worth stopping under for what is over your head. Giant sponges grow up under the lip and French grunts stack themselves into the shade. Spiny lobster back into the crevices. Black grouper hang in the blue below the route, and hawksbills come off the face.

The profile comes out multilevel because of the terrain. The crest starts deep at the south end and shallows the whole way north, so following the reef is the ascent, and the dive finishes over living coral in about eight metres of water instead of hanging on a line in open blue. Divers who come up onto the reef top for the safety stop often find as much on it as on the wall face.

What ends the dive is your no-decompression limit. The deep segment comes early and spends most of it while the cylinder is still nearly full, which is why boats often run this reef on the first tank.

At Santa Rosa the reef above the drop is as much the dive as the drop itself. Swim-throughs lead between the wall and the sand at the depth you are already diving, so taking a passage adds no depth, and a vertical face runs alongside the whole route.

It sits on the mid-coast, where neighbouring reefs mostly stop near eighteen metres and are dived for their fish. Here the coral structure and a wall share one tank.

The 1996 decree that created the national park lists Santa Rosa among its most important reefs1. Wall and Reef are the names dive shops use for the same place.

Say which version you want when you book. The wall and the shallow Santa Rosa Reef run on separate departures, and an Open Water diver who would rather stay above eighteen metres is asking for the shallow one.

This is one of the busiest reefs in the park in peak season, with several operators on the same moorings on the morning departures. Afternoons are generally quieter, though some shops run the shallow profile in the afternoon slot and others the full wall, so ask which one the departure does.

Nitrox suits the profile, because the no-decompression limit ends the dive before the gas does. A dive computer is required, and a surface marker is strongly recommended for the boat traffic above the reef.

A vertical face shows no change in depth, so you can sink six metres below your plan without noticing. Agree a maximum in the briefing and hold it off the computer, because the wall gives you nothing to judge by.