If you take the B6270 road from Nateby that leads up into the hills and over into Yorkshire (heading toward Keld) you will soon find yourself going into Swaledale. OK, so we are not in the Eden Valley but it is close! Not far down the road (see map), on the right hand side you will see miles of open moorland into which several valleys have been carved by small rivers. One of these rivers, Little Sleddale Beck, is well worth a visit if you like some interesting geology, a steep sided valley and the opportunity to do a bit of wild swimming.
The best place is a small waterfall with a deep plunge-pool that is only about a mile or so from the road. From here you can walk for miles up into the hills or loop back to the road by alternative routes. Some enclosed land lies between the road and the open moorland, so using the shooting road visible of the map is the best in and out for you.
In the summer the water in the beck gets quite warm and the pool beneath the waterfall is deep enough and wide enough for a decent swim. Go during the middle of the day whilst the sun is high as the deep sides of the valley cast you into shade later in the day.
Here's a video of what the pool was like in the summer of 2021. A great place if you want to get away from the masses though not as many options for swimming as Janny Woods in nearby Mallerstang.