The wonderful Victoria Falls in Zimbabwe. You can visit the waterfalls either from the Zambian side or from Zimbabwe. If you go to Zambia, you are on top of the plateau, where the water from the Zambesi drops down. Here you can swim in the famous Devil's Pool.
Here is our post about the Devil's Pool: https://steemit.com/wafrica/@roadtrips/africa-18-swimming-in-the-world-s-most-thrilling-infinity-pool-the-devil-s-pool
Truly magnificent!