The cave of sleeping sharks was a water phenomenon, it is a fairly small coral cavern, open one side, on the other there was a small opening not enough to swim through but enough for water from currents to flow at a certain speed, as we know sharks do not sleep they do not have flotation bladders so they have to keep moving at all times, so water can come in their gills, at this cave the flow allowed the water to pass through their gills with no swimming effort. I have visited this dive site in the past and got to see some but not a lot of them. A few years ago to date, the currents, water movements, storms, have allowed sand to rise not permiting the water flow with as much speed as before. There are not much sharks here due to the warm waters and shallow reefs (50ft). Like Ben mentions we do get to see nurse sharks, from babies to bigger ones.
Hope this info was helpful.