Completing his course at the Flinders Naval Depot, Sheean was posted to the Garden Island naval base HMAS "Penguin" in Sydney Harbour on 11 May. During his time with "Penguin", he was berthed on HMAS "Kuttabul", a Sydney ferry requisitioned for use as a barracks ship. Granted a period of leave later that month, he returned home to Tasmania. While he was on leave, Japanese midget submarines attacked Sydney Harbour and sank "Kuttabul" on 31 May. Returning to Sydney eleven days after the raid, Sheean joined the newly commissioned HMAS "Armidale" as an Oerlikon anti-aircraft gun loader.