Some opinions on swimming for long distance running here
http://www.ultrunr.com/swim.html
Some opinions on swimming for long distance running here
http://www.ultrunr.com/swim.html
I do a one mile swim every morning before work and a longer swim at weekends and have done this for the past 15 years. I used to do lots of long distance fell races but I never really needed to run more than 30/35 miles per week as long as I kept the swimming up. I had fewer injuries and fresher legs as a result of it.