I've used to do semi-competitive swimming as a child. Honestly one of the worst (as in boring, great for health and fixed my scoliosis) types of sport to do for an agitated child who wants to explore the world.

For an hour and a half you do laps while staring at the tiles on the bottom of your olympic pool. Would spend the entire time memorizing every crack on the tiles as well as doing entire video game playthroughs in my head lol