Dangerous Reef

The mooring sits over the southern caverns, and most dives begin there. The caverns lie at 7 to 10 metres, never reach far into the reef and always lead back out in a semicircle, so each pass ends in open water within a few fin strokes. Just west of them a small, dense coral garden grows along the wall, a favourite stop for photographers; east of them large coral rocks sit on the sand with their residents tucked underneath.

From the caverns the dive follows either wall north. The eastern and western walls are equally rich in coral, with overhangs and openings, so guides choose whichever side the sun is on. Both walls drop to a sloping sand seabed at about 20 metres, and the route ends at the coral garden and coral towers of the northern tip.

The reef's own length is what shapes the dive: 410 metres of horseshoe shelter the water behind it from wind and waves, and the area beneath the southern moorings stays calm even when the walls see flow. That calm is why boats moor here overnight and why the reef doubles as a night-dive site, with the short caverns as the draw after dark.

The name promises a hazard the reef does not deliver. Sharks would often be found sleeping in the caves to the south, and that is the whole origin of the label.

The caverns are short daylight swim-throughs that loop back out, yet they are an overhead: stay within natural light, keep the trim level and leave any deeper penetration alone. Current, where there is any, is felt on the walls, and how much of it depends on the day and the season, so ask the guide which side is easier before descending. Liveaboard trips are the usual way to reach the reef.

After dark the passages fill with torch beams from every boat on the mooring. Keep your buddy in sight and your own beam low and steady, because divers will be swimming through in every direction.