Whether it’s swimming, running, or biking, make sure you are doing a proper warm down. Most masters swim teams I have been on do a lousy job implementing a warm down into workouts. It’s especially important after you have done sprints and large-effort swims to do at least a few lengths of easy swimming before you leave the pool. In these workouts, you will actually be building up more lactic acid and taxing your muscles more than doing longer distances.
A solid warm down after a workout or race is essential to continuing success in the swim. This will keep your energy up for your next workout, reduce the lactic acid in your bloodstream, and help to keep you injury-free. Typically, 200 yards or so will be enough, but the key here is listening to your body!