Seas and oceans cover 71 % of the earth’s surface and they are home to 80% of all life found on the planet . Among the different components of marine life, the phylum Cnidaria (formerly Coelenterata) has been reported to be responsible for more envenomations than any other marine phylum. It is believed that 2% of its known 11000 species are venomous to humans. Incidents caused by jellyfish are common all around the globe, with serious manifestations and occasional deaths reported in some countries. The Australian box jellyfish, Chironex fleckeri , has been reported to be very dangerous to humans, as contact with its tentacles can provoke immediate cardiovascular collapse and death within minutes. Though other volumes on venomous marine fauna are available, this is the first comprehensive book focusing on venomous marine cnidarians. It is a valuable text-cum-reference resource for researchers, teachers and students of various disciplines, including fisheries science, marine biotechnology and marine biology and for university and college libraries. It is also a useful guide for beachgoers, divers, physicians and environmentalists.