Mahony first played hurling to a high standard as a student at
De La Salle College in
Waterford. He lined out in all grades, including the
Dr Harty Cup. Mahony later played with
University College Cork. At club level, Sheahan first played for
Ballygunner at juvenile and underage levels, winning back-to-back Waterford MHC titles in 2017 and 2018. He eventually progressed to adult level and, after a year with the
intermediate team, he won his first
Waterford SHC medal in 2020. It was the first of five successive Waterford SHC titles for Mahony. He has also won three
Munster Club SHC titles and was at full-forward for Ballygunner's defeat of
Ballyhale Shamrocks in the
2022 All-Ireland club final. Mahony first played for
Waterford as a member of the
minor team in 2018. He later progressed to the
under-20 team. Mahony made his
senior team debut during the
2023 National Hurling League. ==Personal life==