A swimming machine is a device that allows a user to swim against a current in a body of water. The swimming machine is usually an enclosed space filled with water; a pump or series of jets propels water from one size of the enclosure, forcing it toward the other end of the enclosure. The swimmer then enters the body of water and swims against the current, essentially swimming in place. The purpose of a swimming machine is to allow a swimmer to swim in a small enclosure that does not take up as much space or financial commitment as a full-sized swimming pool.
Early models of the swimming machine used pumps and jets to propel the water toward the swimmer. This was effective at creating resistance, which allowed the swimmer to swim without reaching the walls, but the moving water created turbulence that created a swimming environment that was considered to be unnatural and difficult to swim through. The usefulness of the swimming machine outweighed the drawbacks, and for a time, these models were the most common swimming machine models available.
The turbulence issues were eventually addressed by the introduction of propeller-driven systems that moved the water with far less turbulence. The cost of such designs were significantly more, however, until more affordable models were developed. Several versions of the propeller-driven models have been developed, each one aimed at reducing cost and decreasing the amount of turbulence the swimmer will experience while in the device. Hybrid models are also available; these combine the propeller-driven system with jets and pumps to create a powerful stream useful for swimming. Other models employ the use of a tether system that can be used in any pool without the use of a pump, but these models are not as effective as other methods.
Swimming machines are often built into a large enclosure that is smaller than a full sized pool. The swimming machine enclosure is usually about 10 to 15 feet long (3.04 to 4.6 meters) and anywhere from 6 to 10 feet wide (1.82 to 3.04 meters). The depth of the swimming enclosure can vary from model to model, but they are usually not much deeper than 5 feet (1.52 meters). The propulsion devices are often built into the walls of the enclosure, though some models do have external enclosures for the propulsion apparatuses and any power controls.
