[6][4] Beginning a military career after college graduation, he was a member of the United States Airforce from 1951 to 1956, where he served as a Communications Officer with the rank of first Lieutenant.

[4][1] Duncan's Pugent Sound University swimming teams had 15 top five finishes at National Championships in NCAA Division II and the former NAIA conference.

Most notably, while at Puget Sound, Duncan coached 1968 Olympic Backstroke and Medley gold medalist Kaye Hall Greff, one of his most recognized women swimmers.

David Haynes, a Duncan swimmer from 1983-1987, was Puget Sound's 100 and 200 butterfly record holder, and a 1986-7 Ben Cheney Male Athlete of the Year.

[1] Duncan also coached 1990 Puget Sound graduate and freestyler Bob Kabacy, and 1976 NCAA Division II 100- and 200-yard backstroke national champion Dan Seelye.

[8] Melissa Loun, Sharie Juckelund, and Jill Rutledge swam for Duncan on the 1988-89 Women's swim team that won the NAIA National Championship that year, and each were voted to the CSCAA 100 greatest swimmers list.

For forty years, he lived in a beach house on Puget Sound in Wauna, Washington, East of Tacoma, where he became an ardent boater.