At the 1964 Summer Olympics, eighteen swimming events were contested, ten for men and eight for women. There were a total of 405 participants from 42 countries competing. For the first time, the 4×100 metres freestyle relay for men and the 400 metres individual medley for both men and women were contested. Olympic records were broken in all events and the world record was broken in ten events. This competition also marked the debut of electronic touchpads for timing. 15-year-old Sharon Stouder won four medals, three of them gold.