A swimming pool, also called a pool, was an installation filled with water where one could swim or wade. (TNG: "Conundrum") Water polo was also played in a swimming pool. (ENT: "Vox Sola", "The Catwalk")
In 2151, Jonathan Archer expressed his disappointment that there wasn't a pool on Enterprise NX-01 after Malcolm Reed caught a ball he'd thrown to him. (ENT: "Strange New World")
While watching a water polo game with Archer, Trip Tucker asked him how deep the pool was. Archer said it was "deep enough so that no one can touch the bottom." When the captain defined the sport as a combination of basketball, swimming and wrestling, Tucker quipped, "And I thought it was just a bunch of guys screwing around in a pool." Shortly after, Archer asked him if it would be practical to add a pool to Enterprise, but the chief engineer said it might be a problem if, for instance, the gravity plating went offline. (ENT: "Vox Sola")
As a child, Kathryn Janeway was afraid of the ocean, preferring to swim in a pool or a pond because she knew what was below her. (VOY: "Good Shepherd")
In 2269, Nyota Uhura initially mistook an urn which a missing USS Enterprise landing party was drowning in for a pool or a tub. (TAS: "The Lorelei Signal")
In 2368, Kristin suffered amnesia while receiving treatment for her torn ligaments in the USS Enterprise-D's sickbay. Under the mistaken impression that there was an actual swimming pool somewhere on the ship, she asked Doctor Beverly Crusher if she could borrow some clothing from her until she figured out where the pool was. In reality, she had been cliff diving in the holodeck. (TNG: "Conundrum")