Would you like to swim at the edge of a waterfall? You can do exactly that at Victoria Falls located in southern Africa between the countries of Zambia and Zimbabwe. The falls are, by some measures, the largest waterfall in the world. From September to December, due to low water levels, it is possible to swim at the edge of the falls in a naturally formed safe pool called Devil's Pool, accessed via Livingstone Island.
As I see those guys are standing on the bottom, not swimming... If so it's almost fully safe.
Thank you dominixe for the photos. They help very much to crown the impression! :)