Exercising in an aquatic weight-free environment provides a superior cardiovascular workout without muscle or joint stress.
People also find swimming against a current more enjoyable and exhilarating.
The major difference between swimming in still water and swimming against a current is that swimming against a current is more fun. In still water, the faster you swim the faster you go. In an Endless Pool, you simply relax and swim just fast enough to stay with the water speed that you select. In this way, you swim in place against a smooth current. Any time you want to stop swimming, you just stand up in the waist deep water.