On the morning of 10 September 1944, two Japanese swam from Saipan and succeeded in climbing aboard one of the moored seaplanes undetected. They proceeded to blow the plane up with hand grenades, and "Onslow" dispatched a boat to assist the planes crew. The boat was driven back under fire, but two additional boats joined in and they were then able to reach the plane and kill the boarders. However, gunfire set the plane's fuel ablaze, destroying it, although its crew was saved.