Swimming in Walden Pond sounds like fun. Glad to see you off the treadmill.
I got a wonderful guided tour of Walden Pond when I was in Boston last year. Guy is a geology professor and has written a couple books. It was pretty cold that day though, definitely not a swimming day!
Someday, I'd love to swim there, just because.
Swimming outside is the only good thing about summer weather. I'm daydreaming of snow and skiing.