The AE2 Submarine was built by the British and then sold to Australia. It therefore was towed to Darwin where it was used for a short time until it was then towed back through the Suez canal to join the British Navy when World War 1 started. It was 55m long and required a crew of 35 with 3 officers to sail it.
It had none of the communications and detection equipment of today's submarines but was state of the art for its time. So there was no sonar or radar which meant reliance on compass and periscope for navigation, no ventilation so could only stay below the surface for an absolute maximum time of 18 hours and it ran on diesel supported batteries.
Its arsenal comprised about 8 to 10 torpedos.
Churchill developed a plan to attack the Turks on the 18th March 1915 through the Dardenelle Straits however despite a massive naval fleet there were significant losses to the British fleet due to the well fortified Turkish defences comprising significant underwater mines. Three battleships were sunk within a matter of hours and the decision to withdraw and retreat was made.
Captain Dacre Stoker an Irish born British naval commander was seconded to the Australian Navy to command the AE2 along with an Australian crew. Captain Stoker was known to have spent some time lobbying the Australian parliament to have the AE2 taken into battle to assist the British.
The Gallipoli Campaign
When this campaign was envisaged the mission given to the AE2 was to get into the Narrows of the Dardenelles and "run amok". There was no plan for getting out. The Turkish underwater defences were reknowned to be impenetrable and the Turkish land positions and navy were also extensive in the Dardenelles, so essentially this was a 'mission impossible'.