Scientists have mapped the wreck of a ship that sank in Hobart's River Derwent after it ran into and demolished part of the Tasman Bridge in 1975.

The 135-metre-long bulk carrier MV Lake Illawarra ran into several pylons of the bridge causing a large section to collapse onto the ship.

Twelve people were killed in the accident, including seven crew members and five people who were in four cars, which fell 45 metres into the river after driving off the broken bridge.

It was one of Tasmania's most deadly disasters.

CSIRO hydrographer Stuart Edwards said the wreck has been lying in 34 metres of water for almost 40 years.

"MV Lake Illawarra was... on the southern side of the Tasman Bridge, with the top of the wreck at 14 metres below the river's surface and the bow facing towards the suburb of Rose Bay," he said.

"It took us around an hour to map the shipwreck."

The images were produced using shallow water sonar technology on board the Institute for Marine and Antarctic Studies (IMAS) vessel Morana.

The $300,000 high-resolution multibeam echo sounder is a mobile piece of equipment that can be lifted by a single person and can be attached to almost any vessel.

Scientists hope to use the technology for a number of other applications.

Team leader Dr Tara Martin said all the data her team collected would be made public.

"Hydrography is a relatively new science and over the past 200 or so years we've gone from using lines with weights to determine the depth of river beds and the ocean floor, to advanced sonar that can map in 3D," she said.