A swimming pool, swimming bath, wading pool, paddling pool, or simply a pool, is a container filled with water intended for swimming or water-based recreation. There are many standard sizes; the largest is the Olympic-size swimming pool. A pool can be built either above or in the ground, and from materials such as concrete (also known as gunite), metal, plastic or fiberglass. Pools that may be used by many people or by the general public are called public, while pools used exclusively by a few people or in a home are called private. Many health clubs, fitness centers and private clubs have public pools used mostly for exercise. Many hotels and massage parlors have public pools for relaxation. 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.
Contributions by Graham87, Patrick, and Plugwash.