'Rimau was an Allied special forces attack on Japanese shipping in the harbour of Singapore by men of the 'Z' Special Unit as a successor to the successful 'Jaywick' (10/15 October 1944).

'Rimau' was led by the officer behind 'Jaywick', Lieutenant Colonel Ivan Lyon of the Gordon Highlanders. The object of 'Rimau' (originally 'Hornbill') was to sink Japanese shipping with limpet mines after the men of the attacking party had gained access to the harbour in 'sleeping beauty' motorised semi-submersible canoes.

Lyon led a 'Z' Force contingent of 21 men who departed Australia on board the British submarine Porpoise on 11 September. When it reached the island of Merapas, which was to be the forward base, the expedition found that the island was inhabited. To ensure that the party’s stores remained undiscovered by the islanders, one of the submarine’s officers, Lieutenant Walter Carey, remained on Merapas as a guard. The force then commandeered a Malay junk named Mustika. Sequestering the Malay crew aboard the submarine, the 'Z' Special Unit party transferred its equipment to the junk and Porpoise departed. Lyon decided to leave three more men with Carey.

Meanwhile, Mustika neared its target. On 10 October, the day planned for the attack, a Japanese patrol boat challenged Mustika and one of the persons on board opened fire. The party’s cover blown, Lyon had no option but to abort the mission. After blowing up the junk and the 'sleeping beauties', Lyon ordered his men back to Merapas while Lyon led a small force of six other men into Singapore harbour, where they are believed to have sunk three ships. Lyon and 12 others were killed in action soon after this, and the remaining 10 men were captured and later beheaded in July 1945.