Sitting on the silty floor of Turkey's Sea of Marmara since being sunk almost a century ago during the Gallipoli campaign, the AE2 remained undiscovered until 1998.

Now, after a decade of planning, the $5 million project to film inside the submarine has finally delivered the first look inside the cramped interior of the AE2 since she was scuttled 99 years ago.

Working with Turkish colleagues, the Australian researchers used a high-definition underwater camera designed by Defence Science and Technology researchers at Port Melbourne and tested in Geelong's Corio Bay.

The footage shows the 700-tonne E-class submarine, the first to successfully penetrate the strategically important Dardanelles, has been well preserved with only minimal damage from trawlers. Resting 73 metres below the surface, the submarine is covered with silt and sea life. The camera and lighting system entered through the submarine's partially open hatch.

Inside, the features of the engine room and control room are clear, with the steering wheel piles, valves and a ladder all recognisable. There is even a pair of plimsolls neatly stored on a shelf.

''Much of the AE2 is still in beautiful condition,'' said Australian historian Hugh Dolan, who was among the expedition organisers.

The AE2 was scuttled on April 30, 1915 after managing to dodge Turkish mines and torpedoes for five days. During that time they sank a Turkish gunboat.

Her commander, H. G. "Dacre" Stoker, and crew of 32 Australians and Britons were taken prisoner after a torpedo from the Ottoman boat Sultanhisar fatally damaged the submarine's hull.

Sometimes known as ''the silent ANZAC'', some historians argue the AE2's dramatic story was overshadowed by the legend of the ANZAC landings.

''It's remarkable how few people know about the adventure that Stoker and his crew and the boat undertook ,'' said Dr Roger Neill from the Defence Science and Technology Organisation. ''This happened on the first ANZAC Day.''

The submarine began an audacious mission to enter the strategically important Sea of Marmara soon after midnight on April 25, 1915. Her mission was to disrupt the Ottoman supply of troops and goods.

Only a week before, another submarine had been destroyed after failing to penetrate what was then one of the most heavily fortified waterways in the world.

Chairman of the AE2 Commemorative Foundation and retired rear admiral Peter Briggs said the AE2 has an important strategic impact on the Gallipoli landings. By penetrating the Dardanelles, the Ottoman fleet became concentrated on stopping the AE2 rather than getting goods and troops to the peninsula via the Sea of Marmara.