Swimming is a traditional pillar of ACS. The various ACS schools have also won the "B" Division (Under-17) Schools' Swimming Championships for 43 consecutive years since the start of the competition in 1960. In 2003 they were beaten by Raffles Institution, an academic and sports rival, but the school won back the title in 2004. ACS has also produced national-level competition swimmers including Ang Peng Siong and more recently, Mark Chay. They have also produced Singapore's first Olympic Champion, Joseph Issac Schooling.