He competed at the 2024 Paris Paralympics, where he won two gold and one silver medal.. [1] Simpson was born with microdeletion syndrome – a chromosomal abnormality and genetic disorder which causes learning delay and physical flow-on effects – which causes his left and right side not to work in unison.

[3] His parents are Bec and Nigel Simpson, who represented and captained the England rugby sevens team for many years.

Callum has a brother Henry, who is a talented water polo player, and is representing Australia in the surf life saving World Championships in 2024.

After strong performances at national swimming championships, he was selected as a member of The Para Flippers Development Squad for 2023.

[2] He is coached by Olympic swimmer Chris Wright at the Flinders Aquatic Academy in Buderim, Queensland.