Gota Marsa Alam

Route C starts with a compass bearing set before you leave the mooring, because the ground between the boat and the two ergs is sand dotted with coral rocks and gives little to navigate by. You swim to the ergs, circle the larger one past its short cave passage, whose openings sit at 8 m and 6 m, and carry on to the wreck of the Legend before returning, about 50 minutes in all. Route B runs from the southern coral garden to the Legend, again around 50 minutes. Route A is the longest at about 60 minutes and the only one rated two stars. It starts at the northern coral garden and keeps the reef on your left shoulder round the northern tip. From there the wall gives safe orientation but is barren and wide, so divers heading for the 5 m caverns on the central reef tongue cut across the seabed on a bearing of 125 degrees instead. The Legend, a wooden vessel that sank beside the reef on 17 October 2002, lies in the channel between the main reef and the larger erg. Her planking rots a little more each year, so the timbers you pass are fading ones, a short swim from the erg's cave passage.

Three kinds of terrain share this one reef: coral gardens at its northern and eastern ends, two pinnacles standing in sand to the south, and a wooden wreck in the channel between them. The cave passage and the caverns open at 5-8 m, so the variety needs no depth. Three routes of 50 to 60 minutes cover different stretches of the 790 m reef: the coral gardens at one end, the ergs and the Legend at the other.

Bring a compass. The sheltered sandy side is hard to read by eye, so take a bearing before you head for the ergs. Current may run through the whole site but is generally moderate; when it flows through the channel between the reef and the ergs, dive Route C in reverse. Big waves form only on the outer side of the reef. The caverns do not lead far into the reef and the cave passage is short, but both are overhead spaces, so dive them within your training and with a guide. The reef takes an overnight mooring, so night dives run, with common lionfish and some octopus. Stonefish lie on the sandy seabed, which makes the sand the place to hover and keep your fins up.