National Swimming Pool Day is observed worldwide on July 11 each year to celebrate the cultural significance and history of swimming pools. The holiday highlights the benefits of swimming for physical and mental health and encourages people to spend time by the pool. Celebrations often include swimming in personal or public pools, hosting pool parties with games, visiting water parks, and purchasing swimwear or pool accessories. The origins of the holiday are believed to date back to 2016 or 2017. Swimming pools have a rich history, with the oldest known public pool, the Great Bath in Mohenjo-Daro, dating back to the 3rd millennium BCE. Today, the United States boasts around 10.4 million home swimming pools, reflecting the popularity of this leisure activity.