Seidler competed in the men's 5 km event at the 2017 World Aquatics Championships in Budapest finishing 42nd.
[2] Seidler competed in the men's 10 km event at the 2019 World Aquatics Championships in Gwangju finishing 32nd.
[3] Seidler won the 10 km bronze medal at the 2021 South African Open Water Swimming Olympic Trials in March 2021.
Seidler runs an open water workshop in Namibia aiming to help unconfident or new swimmers with ocean swimming.
His partner Amica De Jager has represented South Africa at marathon swimming.