A swimming pool, swimming bath, or paddling pool is a container filled with water to enable swimming or other leisure activities. Pools can be sunk into the ground or built above ground (as a freestanding construction or as part of a building or other larger structure). In-ground pools are most commonly constructed from materials such as concrete, natural stone, metal, plastic or fiberglass, and can be of a custom size and shape or built to a standardised size, the largest of which is the Olympic-size swimming pool.

Many health clubs, fitness centers and private clubs have pools used mostly for exercise or recreation. Many towns and cities provide public pools. Many hotels have pools available for their guests to use at their leisure. Educational facilities such as schools and universities occasionally have pools for physical education classes, recreational activities, leisure or competitive athletics such as swimming teams. Hot tubs and spas are pools filled with hot water, used for relaxation or hydrotherapy, and are common in homes, hotels, clubs and massage parlors. Special swimming pools are also used for diving and other water sports, as well as for the training of lifeguards and astronauts.

There are three main types of inground pools. In order of popularity they are: concrete, vinyl-lined and fiberglass.

Concrete pools are truly custom-built and can be formed to virtually any size or shape. These types of pools are often called Gunite or Shotcrete pools because concrete is shot from a gun onto steel-reinforced walls. Once the concrete cures, it's either plastered smooth, painted, finished with a textured aggregate surface or tiled. Alternatively, a smaller percentage of concrete pools are formed and poured in a way similar to a house foundation. This technique, called structural concrete, is often used for pools built into hillsides.

Fiberglass pools are factory-molded into one giant bowl-shaped piece, which is set into the excavated hole by a crane. As a result, fiberglass pools can be installed much faster than other pool types. In some cases, installation takes as little as three days.

Fiberglass pools have a supersmooth gel coat finish that's extremely durable and stain resistant. Unlike concrete, fiberglass pools are nonporous, so they tend to use fewer chemicals and harbor less algae.

However, fiberglass pools come in fewer sizes and shapes than concrete or vinyl pools. And the huge molded pools must be shipped via truck, which are often forced to take long, circuitous delivery routes. "The transportation of oversized loads is regulated by individual states," explains Suzanne Barrows of the Association of Pool and Spa Professionals. "Therefore, truckers will often have to drive around several states to deliver a fiberglass pool."