Stephen A. “Sid” Cassidy began his swimming career in the mid-1960s, earning numerous accolades and becoming an NCAA D1 All-American at North Carolina State University. As an open-water swimmer, he was undefeated for four years on the Ocean City Beach Patrol and was ranked #4 globally as a professional marathon swimmer in 1979. He transitioned to coaching and quickly earned the highest accreditation as a Level V coach from the American Swim Coaches Association.

Cassidy's career has been marked by significant contributions to both pool and open-water swimming. He has held numerous collegiate coaching positions, including leading the University of Miami's men's team to a Big East Conference Championship in 1995 and four consecutive top-ten finishes at the NCAA Division I Championships. He has been named Florida High School Coach of the Year five times during his long tenure at Saint Andrew’s School. As an administrator, Cassidy was instrumental in the inclusion of the 10,000-meter marathon swim in the Beijing 2008 Olympics while serving as chairman of FINA’s Technical Open Water Swimming Committee.