The Bogle–Chandler case refers to the mysterious deaths of Dr. Gilbert Bogle and Margaret Chandler on the banks of the Lane Cove River in Sydney, Australia on 1 January 1963. The case became famous because of the circumstances in which the bodies were found and because the cause of death could not be established. In 2006, Peter Butt, a filmmaker, discovered evidence to suggest the cause of death was hydrogen sulphide (H2S) gas.
https://en.wikipedia.org/wiki/Bogle%E2%80%93Chandler_case