Completely agree with the outcome of regular exercise, but not with the advice of setting an arbitrary goal and sticking to it. Do not start with a mile, friends! Make that the goal of your 12th or 15th or 20th swim, not your first, depending on your starting fitness and comfort in the water.

(A short course pool is usually 25 yards, so 100 yards is 4 lengths but only 2 laps, a lap being down and back. There are 1760 yards to a mile, so it's impossible to do exactly that.)