A jellyfish may have from eight to hundreds of tentacles depending on its species. Jellyfish tentacles also vary greatly in size, from a few feet to over a hundred feet in length.
Tentacles are a jellyfish's hunting apparatus. When prey comes into contact with their tentacles, a venomous reaction occurs, and the prey is stung and poisoned by thousands of barbed nematocysts. The tentacles then bring the prey to the body to be digested.
Tentacles are a jellyfish's main form of defense, and can be used to paralyze or shock a predator, allowing the jellyfish to escape. Some jellyfish such as the Box jellyfish and Irukandji jellyfish are especially toxic and can easily kill other sea life or humans.