While I was riding my bicycle along the banks of the Aare River in Bern, I noticed that there were small groups, then large groups, then dozens of people in swimming suits, most of them barefoot, walking long distances up the bank of the river.
Then I noticed that there were heads bobbing up out of the swift-running turquoise water, much like the photos we used to see of Mao Tse-tung swimming in the Yangtze River, but cleaner.
There are signs all along the shore saying that the Aare is very fast-flowing and dangerous, and suitable only for experienced swimmers. And people are cautioned not to swim alone.
In 2020, the official website of the city of Bern was amended to read: “Due to ‘social distancing’ in Corona times, we have become more accustomed to self-isolation than we would like. However, this does not apply to river swimming. Because: Long distances should never be swum alone — even the best-trained body can suffer weakness from time to time.”

Walking upstream and swimming down
Because of the swift current, there is only one direction you can swim in the Aare, namely downstream, which is why people try to walk up quite a ways so they can have a longer swim down.

Diving in (or not)
The water temperature was only 19 degrees centigrade, so some people took a while to get their courage up. Also, people are encouraged to go in slowly on hot days, so as not to get a sudden shock from the cold water.

Last exit 140 meters
The main thing about swimming in the Aare is that you have to be careful not to miss the last exit on the left bank, otherwise you might get caught up in the weir below the Kirchenfeld Bridge.

Surfboarding on the Aare
It is also possible to do a sort of surfboarding on the Aare. For this purpose, there is a strong, thick rope attached to the Altenbergsteg, which is a low footbridge beneath the much higher Kornhaus Bridge.
I’m not sure exactly how this works, but I think you have to jump off the bridge with your surfboard, grab hold of the rope without losing the board and somehow get up onto the board with the help of the current. The man in my photo is the only one I saw who actually managed to do this, though several others also tried.
My photos in this post are from 2008. I revised the text in 2020.
See more posts on Bern, Switzerland.
See also: The Rhine River in Basel, Switzerland.
I have seen people swimming there also. Not for me though! I am always amazed at how blue the water appears there also.
19 degrees…. No way I would get in!
Me neither. But those folks are tough.