Operation Rimau was a follow-up to the successful "Operation Jaywick", which had taken place in 1943, being a further attack on Japanese shipping at Singapore Harbour. Rimau (Malay for "tiger") was again led by Lieutenant Colonel Ivan Lyon, a British officer on secondment from the Gordon Highlanders. Originally named "Operation Hornbill", the goal of "Rimau" was to sink Japanese shipping by placing limpet mines on ships. It was intended that motorised semi-submersible canoes, known as Sleeping Beauties, would be used to gain access to the harbour.