In 1943, a 28-year-old British officer, Captain (later Major) Ivan Lyon (of the Allied Intelligence Bureau and Gordon Highlanders), and a 61-year-old Australian civilian, Bill Reynolds, devised a plan to attack Japanese shipping in Singapore Harbour.

Folboats were essential for training the prospective operatives, however only two; a one-man and a two-man were found to be suitable after a thorough search in Australia by Military personnel.

These were bought on the spot from the folboat builder Walter Hoehn after a test run on the Yarra River, Alphington by the head of the Inter Allied Services Department Colonel Mott and Major Moneypenny.

[1] Reynolds was in possession of a 21.3-metre (70 ft) Japanese coastal fish carrier, Kofuku Maru 幸福丸, which he had used to evacuate refugees from Singapore and its neighboring islands.

Aboard was a complement from Z Special Unit of three British and eleven Australian personnel, comprising: On 13 August 1943, Krait left Thursday Island for Exmouth Gulf, Western Australia, where it was refuelled and repairs were undertaken.

Not only did the repairs cause delays in departure, but the folboats, manufactured by Harris Lebus and designated as model MKI**, which had been specially ordered for the attack by Lyon from England only arrived at the last minute.

The men stained their skin brown with dye to appear more Asiatic and were meticulous in what sort of rubbish they threw overboard, lest a trail of European garbage arouse suspicion.

During the journey, they suffered a snapped prop shaft, which had to be repaired by a passing US submarine, while the heavily laden craft was later almost sunk by a force nine gale.

That night, six men left the boat and paddled 50 kilometres (31 mi) with folboats to establish a forward base in a cave on a small island near the harbour.

Their return to Australia was mostly uneventful, except for a tense incident in the Lombok Strait when the ship was closely approached by Japanese auxiliary minesweeper Wa-102 on patrol; however Krait was not challenged.