Entrance chamber over 300 metres long leads to a 180 metre long lake. The cave then consists of a single, straight tunnel more than six kilometres long, of which more than 90% is underwater. From the entrance lake the first sump is about one kilometre length to the air-filled Rockfall Chamber. Dive gear must be transported over the Rockfall Chamber to the second sump, which is 2.5 kilometres in length. The second sump leads to another chamber named Toad Hall. Dive gear must be carried across Toad Hall to reach the third and final sump, which is 1.8 kilometres in length. Cocklebiddy has been the object of numerous cave diving expeditions over the years. Accounts of two of the more notable recent expeditions in 1995 and 1997 are given here.