A half mile in a pool is equals to 18 laps for a short course and nine laps for a long course. This is for a 50 meter long pool with a width of 25 yards.
In a short course, a lap is defined as the width of the pool and back, or 50 yards. Down the length of the pool and back or 100 meters is taken to be one lap in a long course.
Working out in a pool is excellent for maintaining muscular-skeletal and cardiovascular fitness. To minimize fatigue and maximize the number of muscle groups used while swimming laps, alternating between backstroke, breaststroke and freestyle helps. Mayo Clinic's Michael Joyner, M.D. proposes 30 minutes of pool running and 30 minutes of lap swimming as the perfect pool workout.