The Coahuilan box turtle (Terrapene coahuila), or aquatic box turtle, is an endangered species of turtle in the Emydidae family. Unlike the other members of the genus Terrapene, this turtle spends roughly 90% of its time in water.It is a close relative to the common box turtle (T. carolina). Researchers have therefore suggested that it developed from a nonaquatic species in order to survive in the desert springs of Cuatro Ciénegas.