Aliwal Shoal

The Aliwal Shoal is a rocky reef which is the remains of an ancient sand dune approximately 5km off the coast of KwaZulu-Natal, South Africa. The reef is inhabited by many kinds of hard and soft corals and a variety of tropical and subtropical fish species. Aliwal Shoal was named after the near-sinking of the 3 Masted vessel "Aliwal", captained by James Anderson, in 1849. There are two wrecks near the reef that are popular recreational dive sites. The Norwegian bulk carrier, the MV Produce which sank in 1974, and the SS Nebo which sank in 1884. Aliwal Shoal has diverse marine life including large predators and is popular as a recreational scuba diving destination. The Shoal is known especially for its abundance of Grey nurse sharks (known locally as ragged tooth sharks or "raggies") between July and November when the sharks congregate there to mate.MorphologyAliwal shoal is part of a large offshore reef complex. The narrow ridge parallel to the coastline about 5km offshore, more specifically referred to as the Crown, is the part usually referred to as Aliwal shoal, and this area is inside the sanctuary zone of the Marine Protected Area. The shallowest part, extending to within 6m of the surface, is at the north end of the Crown. To the north the bottom slopes down relatively steeply, and to the sides the slope is less. The shoal is about 380m wide to the north, narrower to the south, and then spreads out towards the coast in the section known as the Ridge. Average depth of the Crown is about 12.5m, and the Ridge is about 19.5m average depth, with a few isolated pinnacles.GeologyThe reef consists of aeolianite with subordinate beachrock. It is thought to be sunken coastline of the late Pleistocene. The type of rock was determined from samples recovered from the hull of the vessel Aimée Lykes, which struck the shoal in 1963, and made it to Durban for repairs.