[1] He trained with coach George Haines of the Santa Clara Swim Club.
He later attended Indiana University, where he swam for coach Doc Counsilman's Indiana Hoosiers swimming and diving team in National Collegiate Athletic Association (NCAA) competition from 1963 to 1965.
Trethewey represented the United States at the 1964 Summer Olympics in Tokyo.
[1] He competed in the semifinals of the men's 200-meter breaststroke, recording the ninth-best overall time of 2:34.5.
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