A swim spa is basically a treadmill for swimming. In other words, a swim spa is a small pool / large hot tub with a swim current that allows the user to swim in place.
And with mirrors in place to guide the swimmer, all four basic strokes are possible (breast, back, crawl and butterfly).
Sizes of swim spas can vary, but typical dimensions might be 7 feet by 14 feet.
Besides swimming, swim spas can be used for low-impact underwater running (with a treadmill), water aerobics, strength training (with elastic bands), relaxation, stress relief (with spa jets), and general family fun. Swim spas are also used for a breadth of health therapy application such as arthritis management, injury recovery and weight management. Some more unusual uses have included kayaking training, surf training and animal therapy.
Swim spas can be categorized based on the type of swim current and the type of vessel.
There are two types of swim current systems: 1) spa-type jets and 2) propellers / paddlewheels. Spa-type jets use pumps similar to those used in hot tubs to push water and air through special nozzles to create a swim current. These systems are great for recreational swimmer and family fun. Propeller systems move large quantities of water to create a wide and deep channel of moving water. Some of these systems use grills and turning vanes to smooth the water. These systems typically cost more than jetted systems but are ideal for serious swimmers.
There are also two different types of vessels (or swim spa shells). The most common is the single shell acrylic (or fiberglass) swim spa. These are ideal for outdoor installation. Just crane / fork lift / or roll the swim spa into place, fill it with water and connect up the power -- then you are ready to swim. A less common vessel is the steel panel / vinyl liner swim spa. These are great for indoor installations and more 'finished' outdoor installations. Because these swim spas are modular (i.e. are shipped in pieces) installation takes a little more effort, but the possibilities can be really amazing (i.e. beautiful tile work, custom widths and depths).
A swim spa offers advantages over both hot tubs and swimming pools. Compared to a hot tub, they are larger and have more many more uses. Compared to a swimming pool, you can swim in place 'endlessly' without making flip-turns. And the small footprint makes it easier to maintain and more environmentally friendly. Yet you can still relax after a long day and let the stress melt away. And kids love to play in the swim current. A swim spa offers the best of all worlds.