Shark cage diving is underwater diving or snorkeling where the observer remains inside a protective cage designed to prevent sharks from making contact with the divers. Shark cage diving is used for scientific observation, underwater cinematography, and as a tourist activity. Sharks may be attracted to the vicinity of the cage by the use of bait, in a procedure known as chumming, which has attracted some controversy as it is claimed to potentially alter the natural behaviour of sharks in the vicinity of swimmers.
Similar cages are also used purely as a protective measure for divers working in waters where potentially dangerous shark species are known to be present. In this application the shark-proof cage may be used as a refuge, or as a diving stage during descent and ascent, particularly during staged decompression where the divers may be vulnerable while constrained to a specific depth in mid-water for several minutes. In other applications a mobile cage may be carried by the diver while harvesting organisms such as abalone.
Shark-proof cage
A shark-proof cage is a metal cage used by an underwater diver, to observe dangerous types of sharks up close or to harvest seafood in relative safety. Of the various species of shark, thosee most commonly observed from a cage are the great white shark and the bull shark, which are both known to be aggressive at times. Shark-proof cages are built to withstand being rammed and bitten by sharks, and are intended to protect the user from injury. Cages can provide a visual and tactile deterrent to sharks. Cage-diving allows people to closely monitor sharks for scientific, commercial or recreational purposes, and sometimes interact with them.
The shark-proof cage is also used in the controversial exercise of shark baiting, where tourists are lowered in a cage while the tour guides bait the water to attract sharks or stimulate certain behavior.
Early development
Shark cages were first developed by Jacques Cousteau. Cousteau used a shark cage when producing The Silent World, released in 1956. Australian recreational diver and shark-attack survivor Rodney Fox helped develop a shark-observation cage in the late 1960s. Fox's first design was inspired by a visit to a zoo he made after surviving a near-fatal shark attack in 1963. Film-maker Peter Gimbel was involved in the design of a shark-proof cage for the production of Blue Water, White Death (1971).
Self-propelled version
In 1974, after several reported shark attacks on working divers in Australia, Australian abalone diver James "Jim" Ellis developed a self-propelled cage to protect abalone divers from sharks, which he patented in 1975. Mounting the motor in gimbals in the front of the cage makes the vehicle highly maneuverable. Movement and speed are controlled with a "joystick". The design allowed abalone divers to work without becoming vulnerable to attack. Due to the propulsion system, the divers would exert themselves less and, therefore, might be able to collect molluscs for longer periods. The patent abstract details a self-propelled cage with at least one access opening and a mounting frame that carries both an air motor and a propeller. Buoyant material is attached to the frame so that the cage may be made neutrally buoyant. The diver can control warm water piped to the diver's suit in cold environments. Propulsion was later changed to hydraulics supplied from the boat through the diver's umbilical. The patent expired in 1996, although Ellis continued to make improvements.
A 1975 version of the cage was acquired by the Australian National Maritime Museum in 1988.
Shark-cage diving tourism
During the 2000s, shark-cage diving became more popular as a tourist activity. In South Australia, tourists are taken by boat from Port Lincoln to the Neptune Islands in the southern Spencer Gulf, where they view great white sharks either from a cage tethered to the back of a boat near the surface or from a cage lowered to the seabed. The government considers the activity to be one of South Australia's “iconic nature-based tourism experiences”, which supports 70 jobs and contributes over $11 million to the state's economy.
Shark baiting
Shark baiting is a procedure where the water is baited by chumming with fish or other materials attractive to sharks. Tourists remain inside a shark-proof cage while tour guides bait the waters to attract sharks for the tourists to observe. There have been claims that this could lead to potentially aggressive behavior by the shark population. Some conservation groups, scuba divers, and underwater photographers consider the practice undesirable and potentially dangerous.