Twenty summers ago, my husband, Matt, and I swam down the Aare River in Switzerland with a dog named Arcas. I don't love dogs, which has always felt like a moral failing. But Arcas was special.

Le News, a Swiss news outlet, says, "The Aare River runs through Bern, Switzerland’s charming little capital city. During summer, thousands of locals and visitors jump into the Aare’s milky ...