Pleasant, mellow river swim. There is easy access into the river from grass/shingle on the bend of the river, upstream from the church and just below some little rapids. Quickly deep enough to be out of your depth and swim down/along for a while (although there were a lot of flies on the surface of the water when we went - and swallows trying to catch them!) The current was very slow - unnoticeable in fact - when we went in mid June.
Park in Burnsall village and join the river footpath on the village side, below the bridge by the Red Lion hotel/pub. Follow the path along the side of the river for about half a mile - access spots are just before the steps and very obvious.
There are apparently deeper plunge pools and jumping in places above the little waterfalls, but we didn't walk that far.