HMAS AE1, the first submarine of the Royal Australian Navy, was commissioned in 1914 and marked a significant advancement in Australia's naval capabilities. On September 14, 1914, while on a reconnaissance mission near East New Britain in Papua New Guinea, the submarine went missing. This event took place during the early stages of World War I, a time when the Royal Australian Navy was involved in various operations in the Pacific region. The AE1 had been part of the Australian Naval and Military Expeditionary Force, aiming to seize German possessions in the area. Around 35 crew members were aboard the submarine, and their disappearance raised immediate concerns within the navy and Australian government officials.Extensive searches were conducted after the loss, employing various ships to scour the waters, but no debris or indication of the submarine's fate emerged. The investigation into the incident led to numerous theories about what might have happened—some speculated an accident related to the submarine's machinery while others considered the possibility of an encounter with enemy forces. The loss of HMAS AE1 remains one of Australia's enduring naval mysteries, leading to later inquiries and investigations over the years, but ultimately no conclusive evidence has surfaced regarding its demise. The crew's sacrifice has been memorialized, ensuring that their contribution to the service is not forgotten.