John Finn, longtime L Street Brownie

John Finn spent much of his life swimming in the cold waters near his South Boston home.

A man of routine and an L Street Brownie, Mr. Finn would take his daily dip at the L Street beach after work. He died while swimming there on Friday, relatives said. The cause of death is under investigation. He was 80.

Mr. Finn began swimming with the Brownies as a child and made a habit of diving into the waves every day with the group, which is affiliated with the Curley Community Center. They are known for braving New England waters in all kinds of conditions.

"He would tell us about days where he would have to walk through frozen crusts of ice on the ocean to get to the water he could swim in," said his daughter. "He always said that it kept him young."

Mr. Finn was born in South Boston to immigrants from County Mayo, Ireland. Shortly after graduating from South Boston High School in 1944, he enlisted in the Navy and served two years during World War II. Mr. Finn met his wife, Patricia (Madden), at a gathering at the Gate of Heaven Church in South Boston in 1963, and they married two years later.

A sheet metal worker, he worked with the MBTA for 32 years.

"He would always point out bus stations he worked on when I went to school," said Theresa Finn Dever of Marblehead, one of Mr. Finn's daughters. "He was very handy and proud of his work."

He taught all of his children to swim. "He instilled a love of the beach in all of us," said his daughter. "We would go and have family picnics on the beach."

Mr. Finn was attended Mass daily. He was one of the original members of the Crusaders of Fatima at St. Gabriel Church in Brighton and served as president and treasurer for the St. Vincent de Paul Society at Gate of Heaven.

In addition to his wife and daughter, Mr. Finn leaves three other daughters, Miriam Finn Sherman of Middleborough, Patrice Finn DePasquale of Salem, and Noreen of South Boston; a son, John of Medford; a sister, Patricia Kelley of Sanibel, Fla.; a brother, James of Medford; and five grandchildren.

A funeral Mass will be said today at 10 a.m. in the Gate of Heaven Church. Burial will be at St. Joseph Cemetery in West Roxbury.