Cocklebiddy Cave

Meet the site

Cocklebiddy Cave is the most famous cave dive in Australia and one of the classic long cave penetrations of the world. The CDAA site description summarises it: an entrance chamber over 300 m long opens onto a 180 m lake, beyond which runs a single, straight tunnel more than six kilometres long, more than 90% underwater, following a fault due north. The first sump runs about 1 km to Rockfall Chamber, a large air chamber blocked by a rockpile about 25 m high; the second sump runs 2.5 km to Toad Hall; and the third about 1.8 km further.

Exploration began in the early 1970s. South Australian divers Hugh Morrison, Keith Dekkers and Phil Prust pushed 500 m in 1974 and reached the big chamber at the 1,000 m mark in 1976; the tunnel floor lies at about 13 m with the roof at 0-10 m. In 1983 Cocklebiddy became the world's longest known underwater cave after French and Australian expeditions pushed beyond Toad Hall, and later expeditions (including 1995 and 1997) extended the surveyed length beyond 6 km.

The water is gin-clear, often brackish, and the tunnel is enormous – divers describe elemental darkness in passages so big that lights fail to reach the walls, which can induce a form of agoraphobia. The dry chambers are huge boulder piles that must be crossed carrying equipment.

Access is tightly controlled. CDAA rates the cave Advanced Cave, and divers must apply in writing to DBCA at Esperance at least four weeks ahead with CDAA indemnity forms. It is extraordinarily remote – more than 1,100 km from Perth – with no rescue capability nearby, so every trip is a self-contained expedition. For qualified cave divers, the first sump alone is an unforgettable dive.

What you might see

None visible to most divers – cave-adapted invertebrates (stygofauna) and occasional bacterial growths; megafauna fossils recorded in Nullarbor caves

Location

One of the world's longest underwater cave passages: a single straight tunnel more than 6 km long, over 90% flooded, beneath the Nullarbor near Cocklebiddy Roadhouse.

Facilities nearby

None at the cave. Cocklebiddy Roadhouse nearby: fuel, meals, water, showers, accommodation.