Article 680 of the 2017 National Electrical Code (NEC) provides the requirements for electrical equipment associated with most types of manmade containers of water, whether permanently installed or storable. Excluded are large containers such as lakes formed by dams (the containers themselves aren't manmade). When it comes to understanding what is covered, the definitions in Sec. 680.2 complement the scope defined in Sec. 680.1.
NEC Rules for Pools, Tubs, Fountains, and Spas ― Part 1
An overview of Article 680 of the 2017 NEC