Siphonophores are "colonial jellyfish" which have swimming bells at the top, and tentacles with stinging cells below that help them to catch their prey. Each individual of the colony is specialised for a different function, such as swimming, feeding and reproduction. Some siphonophores can be more than 10 metres long. They are in the phylum Cnidaria, class Hydrozoa and order Siphonophora.