A swim spa is a great alternative to either a larger, more expensive swimming pool or a smaller constrictive hot tub. a swim spa is a machine that allows you to swim continuously against a water current. You never “hit the wall” or have to turn around to continue to swim laps like in a regular pool or a lap pool. Swim spas provide a great swimming exercise workout without a trip to the local pool and using the least amount of space in your garden.