[2][3] He trains at Bond University in Gold Coast, Queensland under the guidance of head coach Chris Mooney.

[4] On day one of swimming competition at the 2022 Commonwealth Games, conducted at Sandwell Aquatics Centre in Birmingham, England starting in July, Southam won a gold medal in the 4×100 metre mixed freestyle relay, contributing a split of 49.21 for the first leg of the preliminaries before being substituted out for William Yang in the final.

[9] For the 2022 Junior Pan Pacific Swimming Championships, held at Veterans Memorial Aquatic Center in August in Honolulu, United States, Southam won the gold medal in the 200 metre freestyle with a Championships record of 1:47.11, breaking former record of 1:47.65 set by Drew Kibler in 2018.

[23] Southam was named to the Team Australia roster in early September for the 2022 World Short Course Championships in Melbourne, which was a little over two months before the start of competition.

[32] In his second event of the evening, he split a 1:41.50 for the third leg of the 4×200 metre freestyle relay to help win the silver medal in an Oceanian, Commonwealth, and Australian record time of 6:46.54.

[37][38] The following month, in the preliminaries of the 200 metre freestyle on day two at the 2023 Australian Swimming Championships, he ranked third and qualified for the final with a time of 1:47.53.

[40] For his first event at the 2023 Australian Swimming Trials in June in Melbourne, Southam placed fifth in the final of the 200 metre freestyle with a 1:47.11.