If you are looking for somewhere to cool off, there are a number of open-air swimming options in Belgium.
If you’re in the North of Belgium: https://www.outdoorswimming.be/
See the Map
And for those in the South of the country: https://environnement.wallonie.be/home/loisirs/baignade.html
See the Map
Please do take care and lather up in sunscreen, but enjoy these various options.
Please do take care and lather up in sunscreen, but enjoy these various options.