[1] Popham commenced swimming as a seven year old as part of his physical therapy program for cerebral palsy.

[1] Popham made his international debut when he represented Australia at the 2018 Pan Pacific Para Swimming Championships in Cairns and won the Men's 100m Freestyle S8 and was a member of the Men's 4x100m Freestyle Relay (34 points) team.

[4] At the 2020 Tokyo Paralympics, Popham won a gold medal in the Men's 100m freestyle S8 with a time of 57.37 Together with Rowan Crothers, Matt Levy and William Martin, he won gold and broke the current World Record for the Men's 4×100 m freestyle 34 pts by almost 2 seconds.

His team won the silver medal in a time of 4:07.70, just over a second behind the winners, RPC, who set a new world record.

He has since been reclassified to an S9 swimmer, a class for athletes with more physical ability compared to the S8 classification.