From 1968 to 1972, Hetzel was an internationally ranked marathon swimmer and swum the English Channel eight times as a solo swimmer and captained six relay crossings that set three new records. He swam the 34K (21-mile) Traversée internationale du lac St-Jean professional race in Canada, the 32K (20-mile) Aswan High Dam competition, 48.2K (30 miles) in Baja California, 48.2K (30 miles) from Point Lookout in New York, and twelve Manhattan Island Marathon Swims as well as coached the famed Doc Counsilman on his English Channel swim. He also attempted a double circumnavigation around Manhattan Island.
He passed away 17 October 2011 in Texas. Joshua Ruiz said of him, "He was an astonishingly humble man and a true American legend. He has left behind God's heavenly bodies of water in exchange for his wings in the sky." Dale Petranech, Honorary Secretary of the International Marathon Swimming Hall of Fame, commented, "We will all miss our friend and fellow swimmer. He made great contributions to marathon swimming. I am sure that we cannot list and appreciate everything that Tommy has accomplished. His eight times across the English Channel and his coaching of several channel swimmers, including coaching great Doc Counsilman, is but a part of his legacy. It is truly a sad day, we will all miss this giant in marathon swimming."
Drury Gallagher, co-founder of the Manhattan Island Swimming Association with Hetzel, remembers, "Tom and I grew up on the shores of the Atlantic Ocean in Rockaway Beach, New York. We had the same teacher and mentor, Joseph Ruddy: a legend, Olympian swimmer and water polo player and member of the International Swimming Hall of Fame. Were it not for Tom, there would be no Manhattan Island Marathon Swim. He was the inspiration and motivational force behind the Manhattan Island Swimming Association. It was through the successes of his English Channel swims that he opened the rivers around Manhattan Island for swimmers from around the world."