Each 'individual' Physalia physalis is composed of a group of polyps specialised for movement, catching prey, feeding and breeding. The individual polyps are dependent on each other for survival, each having a distinct role. A large, purple, gas filled float (the pheumatophore) reaching up to 30 cm in height allows Physalia physalis to float on the surface. The crest running along the top of the pheumatophore acts as a sail when raised. The jellyfish has many digestive polyps (gastrozooids), which hang down and secrete digestive juices onto the prey that has been caught and immobilised by the sting of the long, contractile tentacles (the dactylozooids). The tentacles may hang down several meters and have a bead-like appearance. Each 'bead' contains specialised stinging cells (nematocysts), which produces a debilitating sting.Even though individual Physalia physalis are not an unusual sight on the coasts of Britain and Ireland, mass standings are uncommon, occurring only 3 or 4 times a century (Wilson, 1947). The sting of Physalia physalis causes severe pain, skin lacerations, convulsions, respiratory distress and in some cases death (Williamson et al., 1996). The sting remains potent even after death and the tentacles should not be touched. Portuguese man owar are carnivorous feeding mainly on small crustaceans and larval fish (Kirkpatrick & Pugh, 1984).