Is this really used for swimming? I find no reference to swimming in it online. It is described as a natural pool in the river, in the sense of https://en.m.wikipedia.org/wiki/Stream_pool, and looking at the tagging history of the object, I wonder if the Maproulette mapper misunderstood the natural=pool as a reference to swimming.
https://www.openstreetmap.org/way/606787821/history