Now, I wasn't making a joke (to my tv) and I wasn't venturing a guess. I knew the actual two presidents to which they're referring. That's extreme nerdity (good or bad). Nobody should really know that offhand.
But I've come this far so I might as well go all the way....
I object to the term "skinny dipping" in this instance. It's a bit misleading. "Skinny dipping" is something high school kids do during games of "Truth or Dare"; it's something "Stiffler" would do in "American Pie 8: The Kingdom of the Crystal Skull". John Q. Adams and Teddy Roosevelt swam nude outdoors for exercise and health (it was believed that the shock of cold air and/or cold water was invigorating and good for one's constitution). Let's not degrade their legacy with stupid terms. Next they'll be saying that Archimedes yelled, "Eureka!" and went streaking.