Practically all of the phyla of aquatic animals have some which are dangerous to man. Men may encounter these animals in the course of various activities including surface and subaqua fishing, the installation and handling of equipment in connection with the exploitation of petroleum under the sea, underwater construction and scientific research; and thus be exposed to the risk of accidents. Bathers and subaqua enthusiasts are also exposed to the same risk. Most of the dangerous species inhabit warm or temperate waters.