I did my longest swim to date. I had the day off some I wanted to go swimming in the afternoon when I figured the pool would be relatively empty. Turns out half the pool was blocked off and they were doing lifeguard training. I planned to do a long easy swim. I mostly did half freestyle, half back crawl. I played a little bit with my freestyle trying to be more efficient. I got to 35 laps or about one mile, and still felt good. I decided to go to 42 laps (1.2 miles or half Ironman distance). I still felt good, so I decided to go to 50 laps. I started to get a cramp in my left calf from the flutter kick. I do more flutter kicking when I do backcrawl. I started mixing in backstroke with whip kick. That worked. I got to 50 laps, and still felt good. I continued on to 60 laps, and decided to end it there (about 1.7 miles). It was the longest I had swam by almost 15 laps. It took 1:24, but as I said, I was swiming very easy and relaxed. I also stopped a few times so that I could time a few laps with different strokes. I could have kept going as I was feeling good. I probably could have made it to 2.4 miles (Ironman distance). 
