A swimming machine is a device used in resistance swimming enabling the swimmer to swim in place, usually within the confines of a water tank at least twice as long and twice as wide as an average person with the limbs extended.
A swimming machine is a self-contained swimming apparatus enabling the swimmer to swim in place. The first type, known as a "countercurrent swimming machine," usually consists of a water tank at least twice as long and twice as wide as an average person with the limbs extended.