[6] At Foothill, he led his teams to eight national swimming titles, and five state Junior College championships in water polo.

[8][5] Outstanding swimmers coached by Thornton before he began at U. Cal Berkeley included 1960 and 1964 Olympian Steve Clark, 100-meter freestyle record holder, Gary Ilman, a '64 Olympic medalist in the 100 freestyle who swam for Foothill Junior College, and Canadian Ralph Hutton, a three-time Olympic finalist.

Australian swimmer and 1972 Olympic triple gold medalist Shane Gould trained at the Foothill Aquatic Club during High School.

[4][9][10] During his tenure, members of the team won 48 individual and relay NCAA championships and 108 Pac-10 individual, relay and diving championships,[9][10] Forty-eight of his swimmers competed in the Olympics, winning 14 gold, 10 silver and 5 bronze medals;[10][11] two others won one gold and one silver medal after his retirement.

[12] Outstanding Olympians coached by Thornton included U.S. team member Peter Rocca, and Swedish Olympic team freestylers Bengt Baron, Pelle Holmertz, Par Arvidsson, and Thomas Lejdstrom and freestyle sprinter and 1992 Olympic gold medalist Joel Thomas.

Among other more recent Olympians, he coached world record holder Matt Biondi at Cal, and Anthony Ervin, who won the gold medal in the 50-meter freestyle at the 2000 Sydney Olympics.

[10] He served as president of the American Swimming Coaches Association and on its board of directors, and was a member of the NCAA Rules Committee.