Close-up of the tentacles of a sea anemone waving in the current. Sea anemones are cnidarians, relatives of jellyfish and corals, which use their stinging tentacles to catch prey, typically small fish or crustaceans. They are sessile for all or most of their life, attaching themselves to rocks or other hard substrates with a fleshy basal disc. Although their stinging tentacles can paralyse and kill many small animals, some are immune to their stings, and several species of fish live amongst anemone tentacles, using them as protection from predators. Filmed in the Gulf of Thailand.