These pools have several names; infinity (though this is usually more to do with the side walls, than the swimming), perpetual, endless. All provided by (counter) current machines.
A counter current unit is a high-volume pump providing a flow of water from an outlet on one side of a pool. It can turn a small pool (2m wide x 3m long x 1m deep) into an exercise pool at the touch of a button. You swim against the current for as long as physically possible without needing to turn. Adjusting the current to the swimmers pace to allow swimming in a smooth, even current matched to your ability (the fastest available for those who can swim at 100m per minute). This swimming treadmill is ideal for training, and offers the benefit of being able to mimic an outdoor swim without having the 'false activity' of turns. Multiple counter current units can be installed in one pool (if wide enough, with circa one unit per 2m width / lane). These units are very affordable, starting at circa €10k for a retrofit, or €50k for a small pool build.
Picture taken from www.guncast.com › news › swim-training-pools
