A swimming pool is an artificially constructed open-air basin designed to hold water for swimming or various water sports. This includes water polo pools, wave pools for surfing, and similar pools. They may be open to the sky or covered with an open pavilion. Not included in this category are natural bodies of water, or pools with retention walls of natural materials such as earth, clay, or sand.

The basin is deliberately constructed for water recreation. It can remain open to the sky or have an open pavilion above it while retaining the stated open-air form.

Wave and water-polo pools are included despite their specialized activities. Natural bodies and basins retained by the listed natural earth materials have the explicit exclusion above.