Brian C. Zwaan, a prominent Philadelphia banker beloved for his work in keeping Archbishop John Carroll High School in Radnor open during a time of ongoing financial insecurity, knew how to light up a room. He was a "full-of-life person, a 'you hear him before you see him' kind of guy," according to his close friend Stephen Kincade, who had known Mr. Zwaan since they met in grade school at the former St. Denis School in Havertown.

"Just a great human being; he was everybody's friend," Kincade continued. "Big person; loud, loud voice. Big, big laugh."

Mr. Zwaan, 58, died Monday, July 31, in a swimming accident in the waters off Sea Isle City, N.J., his family said.

He spent his career in banking, serving at Commonwealth, Firstrust, and Citizens Banks before co-founding Penn Liberty Bank in 2004, serving as president until 2016. Since August of last year, when WSFS Bank acquired Penn Liberty, Mr. Zwaan had served as vice president and director of commercial banking in Pennsylvania for WSFS.

Mark Turner, the president of WSFS, wrote in an email of his colleague's "big presence," saying also that he and Mr. Zwaan had bonded over their shared background of being raised in large Catholic families and being reared "by tough nuns, and being street rats." He said he and Mr. Zwaan "shared many common memories of joyous childhoods."

Turner said he and Mr. Zwaan's coworkers were "devastated by Brian's tragic, way-too-soon death."

After meeting with bank colleagues upon learning of Mr. Zwaan's death, Turner described the collective reaction. "Besides the shock and sadness, there was clearly great love and celebration for a real man, a big presence, a great father and friend, a genuine business leader, someone who loved life, a good laugh and who put himself out there always for others and the community."

Mr. Zwaan was instrumental in keeping Carroll's doors open and its admissions up. He and his siblings started the Regina and William Zwaan Scholarship Fund in 2001, following the death of their mother. To honor their parents, who put them all through Catholic school, the siblings furnished the fund with proceeds from bowl-athons and raised upward of $125,000 for the effort. He was a member of the high school's advisory from 1990 to 2011.

Mr. Zwann's daughter Elizabeth Zwaan Milne recalled his outsize personality and signature belly laugh.

"You could pick him out of a dark movie theater immediately," she said. "He was constantly smiling, lighting up the room. He was a major practical joker."

Mr. Zwaan loved the beach and the Poconos and enjoyed listening to Bruce Springsteen, playing golf, and going to Phillies and Eagles games with friends. His daughter said he didn't miss a week of Mass, even bicycling every Sunday to St. Joseph Roman Catholic Church in Sea Isle City, where the family owned a home.

Catholicism played a central role in his life.

"He grew up in that lifestyle and instilled it in all of us," Milne said.

Mr. Zwaan grew up in Havertown, around the corner from Diane Logue, a longtime friend and schoolmate who would become his wife in 1985. He graduated from Carroll in 1976, where he was a member of the National Honor Society and played offensive guard for the football team, earning Catholic All-American recognition. In 1997, he was named a distinguished alumnus.

In 2014, he was among four people honored as distinguished graduates by the Philadelphia Archdiocese whose "achievements and commitment to living a Catholic life best embody the spirit of Catholic education in the archdiocese."

He went on to play football at Lehigh University his freshman year for the Division II national championship team in 1977. After the win, he turned his attention to his studies and earned a degree in accounting. He also earned an M.B.A. at Drexel University.

He was a member of the Advisory Board at Villa Maria Academy High School, where his wife worked as director of special events and from which his three daughters graduated. School officials there lamented his passing.

"He had the uncanny ability to make the person he was talking to feel like the most important person in the room," said Kathy McCartney, Villa Maria's director of advancement. "The world is a sadder place without the jolly, quick-witted, larger-than-life Brian Zwaan."

Milne found that tribute particularly poignant and accurate.

"When he talked to you, he talked to you and was listening fully," she said. "He just made you feel very important."

In addition to his wife and daughter, he is survived by children  Matthew, Sarah, and Margaret Lynn; six sisters; and four brothers.

A viewing for Mr. Zwaan will be held from 5 to 9 p.m. Friday, Aug. 4, at St. Denis Catholic Church, 2401 St. Denis Lane, Havertown. A Funeral Mass at 10 a.m. Saturday, Aug. 5, will also be at St. Denis.

Donations may be made in his name to any of the following schools: Villa Maria Academy, Malvern Preparatory School, St. Norbert's School in Paoli, Archbishop Carroll, or Cardinal John Foley School, formerly St. Denis School of Havertown.