This account is fascinating. It is conceivable that this could have been Waratah. Although the trader in question was stationed at Xora River mouth in 1913, he referred to a 'dangerous coast', implying that the sighting of the large steamer was not necessarily off the Xora. If it had been the Xora, it seems strange that one of Waratah's deckchairs would have drifted some 13 n miles upstream to Coffee Bay. We know that the depth of sea off the St Johns Reef, Bluff Point, (Poenskop), immediately drops to 18m, sharply falling off to 38 - 39m by 0.5 n miles offshore. This would be in keeping with a 'tremendous depth of water runs outside the reefs'. The sharks would have, according to the trader, have prevented survivors from making it onshore (perhaps with the exception of one lad, Staunton, who perished in the Great War).
However, if the Harlow account is true, the conditions were calm at the time of the large steamer disappearing astern. It was certainly not a 'wild night', yet.