An exhibition featuring two wartime shipwrecks that were the subject of decades of speculation will offer a rare glimpse into the tragedy, on the 75th anniversary of the ships' sinking.

For 66 years, the maritime tragedy and mystery laid undiscovered 2,500 metres beneath the ocean's surface, more than 100 kilometres off the Western Australian coast.

The sinking of the HMAS Sydney (II) and German raider HSK Kormoran on November 19, 1941 was considered one of the world's most significant wartime mysteries and sparked decades of speculation.

It remains the Royal Australian Navy's worst naval disaster, with the loss of all 645 men aboard.

Eighty of the Kormoran's 397 crew died during the battle.

In 2008, the shipwrecks were found lying about 20km apart on the seafloor 200km west of Shark Bay, 800km north of Perth.

An extraordinary expedition

A painted gun from HSK Kormoran lay at the bottom of the ocean for decades. ( Supplied: WA Museum )

For the first time, the ships' final resting places can be explored by visitors to the Museum of Geraldton, on the eve of the 75th anniversary of the tragedy.

From great depths: witnessing the wrecks of HMAS Sydney (II) and HSK Kormoran is a collaboration between the WA Museum and Curtin University.

The exhibition features personal accounts, historic photographs, and wartime service records of the ships.

The highlight is a 3-dimensional film of footage captured during the first expedition to the shipwrecks' dark depths in 2015.

For Curtin University researcher Andrew Hutchinson, who grew up in Geraldton, the expedition was a childhood dream come true.

Dr Hutchinson said he became fascinated by HMAS Sydney (II)'s disappearance at a young age.

"The stories about the shipwrecks along that coast are legendary," he said.

"When I was growing up, there were lots and lots of people on that coastline who claimed to have seen the battle occur.

"I grew up with all those stories and … I was very interested.

"It's really quite astonishing that they're the only two warships in history to come together and simultaneously destroy each other.

"That improbability is part of what led to so much speculation about other possible explanations."

An 'incredibly emotional' experience

HMAS Sydney (II) was the subject of one of the world's most significant wartime mysteries. ( Supplied: Sea Power Centre Australia )

Dr Hutchinson and his colleague Andrew Woods managed the technical aspects of the successful expedition, which was five years in the making.

State-of-the-art underwater vehicles filmed 23 hours a day for five days, capturing hundreds of hours of video and hundreds of thousands of images.

Dr Hutchinson said it was an "incredibly emotional" experience.

"To be separated from the wrecks by millions of tonnes of dark, cold water and to know that we were shedding a light … for the first time ever since 1941 was very exciting, very thrilling and very nerve-wracking," he said.

WA Museum chief executive Alec Coles said the exhibition offered visitors the opportunity to explore the most inaccessible site on the Australian Heritage Register.

"What this does, which is quite unique, is to give you a very intimate, very thoughtful and very contemplative opportunity to … be at peace with those sites," he said.

Mr Coles said the exhibition was deeply affecting and a respectful way to mark the 75th anniversary.

"It's a very moving experience," he said.

A book with the same title highlights work by some of Australia's leading scientists, maritime archaeologists and historians to bring the remarkable tale from the seabed to the surface.

The exhibition opens at the Museum of Geraldton on Friday.