Inage Kaihin Park Pool

Admittedly, this coastal water park lies outside Tokyo, but the local station (Inage-Kaigan) can be accessed from Tokyo Station in approximately 40 minutes, making it an easy destination for a day in the sunshine. 13 separate outdoor pools house an abundance of watery attractions, including a wave pool, a water station (like an adventure playground for kids) and Chibikko Pool (kids' water slides and umbrella showers). The highlight is the unimaginatively named Water Slider, a giant pair of chutes, the tallest of which stands 11.4m off the ground. The good news for anyone seeking something a bit more basic is that there's a 50m pool (approximately 1.8m deep), ideal for working on your crawl.

The five minute video below gives you some idea of what the park is like. Keep your volume turned down if don't want to feel as if you're in a supermarket.