Many species of jellyfish are found in Australian coastal waters, some of which are dangerous or even deadly to humans, while the majority are harmless. All have tentalces equiped with nematocysts, or stinging cells. These are used by jellyfish to deliver toxins into their prey. The stinging apparatus consists of a "harpoon" on a thread coiled inside the stinging cell, and attached to a reservoir containing venom. On contact with the victim, the stinging cell discharges its harpoon into the skin and injects venom. Each tentacle may be covered with millions of stinging cells, resulting in a large amount of venom being injected over a wide area.