Common octopus Octopus vulgaris hunting on the sea floor A grouper fish lower right is waiting for prey that might escape The common octopus is a nocturnal predator that hunts fish crustaceans and bivalves It is found worldwide in both temperate and tropical oceans to a depth of metres Like all octopi the common octopus can change colour according to its surroundings by dilating or contracting pigment cells called chromatophores This acts as a form of camouflage from predators Photographed off Bonaire island Netherlands Antilles Caribbean