Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) such as the tiger shark, the blue shark, the bull shark, and the milk shark. The name may be related to the French word for shark, requin, itself of disputed etymology (chien de mer or Latin requiem ('rest'), which would thereby create a cyclic etymology: requiem-requin-requiem. Family members have the usual carcharhiniform characteristics. The eyes are round, and the pectoral fins are completely behind the five gill slits. Most species are viviparous, the young being born fully developed. They vary widely in size, from as little as 69 centimetres (2.26 ft) adult length in the Australian sharpnose shark, up to 5.5 metres (18 ft) adult length in the tiger shark.