There is no definitive answer to this question as it depends on a number of factors, including the definition of a swimming pool. However, according to Guinness World Records, the smallest swimming pool in the world is just 9.84 square feet (0.91 square meters).
This record was set by British company Aqua-Pools, who built a miniature pool measuring just 3.6 meters (11 feet 10 inches) long by 1 meter (3 feet 3 inches) wide. The pool was designed for use in small spaces such as balconies and terraces, and can be installed above or below ground level.
While this may be the smallest swimming pool in the world according to Guinness World Records, there are smaller pools out there that have been built for specific purposes. For example, Japanese company Koto created a tiny plunge pool measuring just 2 square meters (21 square feet), which was designed for use in hotel rooms. And in 2014, US company Endless Pools unveiled their new line of micro-swimming pools that start at less than 2 square meters (22 square feet).
So while there is no definitive answer to the question of what is the smallest swimming pool in the world, it seems that anything under 3square meters (32square feet) could lay claim to this title!