This afternoon exercised “Action Stations” with alternative forms of control, breaking down into Defense watches, which are to be maintained during daylight hours today & tomorrow, when we expect to hit the Cocos Islands, where we will be at our nearest to Jap.[Japanese] held territory this trip.
Just before 1800, an echo from a plane not showing IFF [Identification, Friend or Foe] was obtained on our port quarter at a distance of about 25 miles. The AA[Anti-Aircraft] Armament was brought to the ready & when the plane, which was on a parallel course to ourselves and which had been recognised as a flying boat, probably a Catalina, had closed to 16000 yds a challenge was flashed. There was a certain amount of doubt about the reply but it was established that the wrong answer had been given. By this time the plane was on the port bow & rapidly going away, so no further action could be taken. Noon position, today Wednesday: 7°24’S, 92°16’E.