LOL - you're going to pick up hot women by showing off your biker's upper body development? Now someone will probably post that picture again! Ugh!

I agree, swimming would be a good cool-down. My main worry would be making any post-ride dehydration worse by adding a second workout too soon. Lay off the butterfly and just do freestyle/crawl at 65% effort, and it might actually help prevent soreness after a hard ride.