I've done five 70.3 iron mans. I swam competitively in college and now at 26, I'm a total endorphin freak (runners high) as well (ran the LA marathon 4 times as well as countless others) If I had the time- id consider training to qualify for a full ironman however- that takes incredible dedication, where it's literally a full time job.
I don't skip many swims a day- which is what keeps me lean. I had a period where I stopped swimming for about a month a few years back and gained no joke 25 lbs that month, so it's something I must do, plus I've found it to be my therapy. (I average from 4-6 miles a night)
So I guess that makes two of us!