When Australia's first submarine AE1 exchanged signals with the destroyer HMAS Parramatta in the waters off New Guinea nearly 100 years ago, there was no sign of the disaster to come.
The vessels were on patrol as part of Australia's first but little-known action of World War I to occupy German New Guinea and capture important maritime radio stations.
Parramatta last saw the submarine about 3.20pm on September 14, 1914, and returned to the fleet anchorage nearby that evening to find AE1 had not arrived.
The navy began a search that night. It continued for three days, centred on AE1's last known position near Duke of York Island, near New Britain, and the coastal waters nearby.
But no trace was found of AE1 or the 32 sailors and three officers aboard. AE1's disappearance was the Royal Australian Navy's first major tragedy and remains one of its most enduring mysteries.
The fate of the submarine has been the subject of much research and debate.
The most probable explanation still remains that AE1 hit a reef somewhere around Duke of York Island and sank nearby.
A number of searches have been undertaken by naval and civilian vessels and divers, based on AE1's last known position, its probable course on the day it was lost and information from local islanders and divers.
Much of the work has been driven and co-ordinated by former members of the RAN, particularly former submariners.
It has been documented by the group AE1 Incorporated, which maintains an extensive website about the mystery and continuing search, which has also involved media networks and the WA Maritime Museum.
Now, as the centenary of the loss approaches, the Federal Government says it will start another search in September.
Defence Minister David Johnston said an RAN mine hunter would be sent to search near Mioko Island, south of Duke of York Island.
The search will take into account the circumstances of the vessel's loss, historical records, ocean drift and topography, expert analysis by submariners and engineers and also the oral history of local islanders. The AE1 Incorporated website refers to the islanders' story about the day a "devil fish", (a submarine), approached Mioko Island.
The islanders said the submarine stopped, went backwards and then disappeared, the website says.
The RAN vessel will set up a grid pattern search using sonar, and is to cover an area of about 13sqkm.
AE1 Incorporated president Michael White said the group was pleased and grateful that the navy would resume the search.
But he also sounded a cautionary note, saying that if AE1 lay in a deep part of the nearby channel it would be beyond the limits of the search vessel.