The dreaded tentacles of the Portuguese man-of-war belong to the dactylozooid polyps it contains. Their stinging nematocysts can paralyze small prey and cause immense pain to humans, which is sometimes accompanied by powerful allergic reactions that lead to fever and shock, as well as heart and lung problems. In fact, the toxin exuded by the tentacles of the Portuguese man-of-war is about 75 percent as powerful as the venom of a cobra. Even when they are washed up on the beach, the tentacles remain dangerous and should not be touched with bare skin.