Terry observes that we probably aren't lacking stroke rate. So the idea is to save strokes and become more efficient. A reasonably good swimmer can cover 50 yard repeats in 40 strokes and 40 seconds. If you just swim harder, your time might drop to 35 seconds but your stroke rate may increase to, say, 44. Soon, your heartrate will rise and your technique will likely fall apart, too.
Lower score equals greater efficiency.
This stroke efficiency objective ties right in with no sweat swimming which is a low intensity approach to swimming faster. Olympic champion, Alexander Popov is cited numerous times as a swimmer who's main training concern is technique refinement, mostly below his anaerobic threshold. So, slow down and practice precisely. It's working for me. I'm doing the Ironman Florida, November 4th, 2000.