mudskipper, name for several fishes of the genus Periophthalmus, of the goby family, found in coastal waters of the Indian and Pacific oceans. They live chiefly on mud flats and in brackish mangrove swamps and are adapted for remaining on dry land when the tide goes out. They have no special air-breathing organs, but absorb oxygen through the skin and gill chambers as long as these remain moist. When out of water, mudskippers use the fleshy bases of their pectoral fins for propulsion on the ground, and members of the larger species can skip faster than a person can move. The mudskipper's diet includes insects and small fish. About 8 in. (20 cm) long, it is olive brown, often with bluish markings. Its protruding, mobile eyes give it a froglike appearance. It is classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Perciformes, family Gobiidae.