The Olympics highlight the reality that science changes, and it's a mistake to become complacent about science. To see the impact, here's a great graphic on 100 meter freestyle outcomes in Olympic history. The results highlight the impact of changes wrought by improving the science of swimming, not to mention conditioning, nutrition and weight training.
Examples of change? I can say from experience that back in the old days of the early 1970s, typical swim team coaching in Illinois included the idea of kicking very little in freestyle races, and no one was doing a dolphin kick off the blocks or coming out of turns. Today, it's relatively the opposite as swimmers use a dolphin kick off the blocks and off turns, and any observer can see that a powerful kick is a significant component of great freestyle swimming. Doc Counsilman was the main researcher and writer of the book on swimming, first in 1968 and then a whole new book in 1994. The research was conducted in pools using scuba gear, cameras and lots of work. Today, great advice is online and free, with plenty of videos and science papers to help create the next set of Olympic winners.