Breen was born in
Buffalo, New York. He was a champion rower for
Bishop Timon High School in
Buffalo, and the West Side Rowing Club.
Cortland State Breen attended
Cortland State University, then known as Cortland State Teachers College, where he swam for Hall of Fame Coach
James "Doc" Counsilman, from around 1952-1956. On May 15, 1956, as a college Senior, he won his signature event, the 1500 meter freestyle at the Eastern Intercollegiate Swimming Championships at Cornell's Teagle Hall Pool in a time of 17:44.5. He completed the swim 140 yards ahead of the second place competitor. The event was held in a 25-yard pool. His time in the event, the whe he had won it the prior year was a 19:00.4. Breen was an All American three times while at Cortland State, and won All American honors with the American Athletic Union as well. During Counsilman's tenure as coach at Cortland State from 1952-1957, which included Breen's time as a competitor, the swim team had a noteworthy record of 35-5 in dual meets.
1500-meter world record According to EBSCO his breakthrough moment, and greatest single effort, was his 1500-meter Long Course World Record of 18:05.9 at the May 3, 1956 U.S. AAU Indoor Championship at Yale, referred to by Ohio State Coach Mike Peppe as “the single most brilliant effort in swimming since I’ve been coaching.” Breen reduced the standing world record by a substantial 13.1 seconds, and incredibly completed his swim a full 1:18, ahead of the second-place finisher, Frank Brunell, who had been an American National Champion many times. No prior swimmer had ever completed an event so far ahead of the second-place finisher in the history of the U.S. Nationals. ==World competitor==