A swimming pool, swimming bath, wading pool, paddling pool, or simply a pool, is a man-made container filled with water intended for swimming or other water-based recreation. A pool can be built either above or in-ground, and be constructed from materials such as concrete (also known as gunite), metal, plastic or fiberglass. Pools can be decorative or custom shape and size, or they may be standard sizes, the largest of which is the Olympic-size swimming pool.
Many health clubs such as the YMCA, fitness centers and private clubs have public pools used mostly for exercise. Many hotels have pools available for their guests. Educational facilities such as schools and universities occasionally have pools for swimming or physical education classes, or competitive athletics such as swim team. Hot tubs and spas are pools with hot water, used for relaxation or therapy, and are common in homes, hotels, clubs and massage parlors. Swimming pools are also used for diving and other water sports, as well as for the training of lifeguards and astronauts.