The MV Lake Illawarra crashed into pylons of the Tasman Bridge in Hobart, sinking 34 metres below where it has remained for the past 39 years.

Twelve people died when a large section of the bridge came crashing down, including seven crew members and five occupants of four cars, which fell to the icy depths below.

CSIRO Geophysical Survey and Mapping hydrographers Matt Boyd and Stuart Edwards and Institute for Marine and Antarctic Studies leader Andrew Pender decided to map the shipwreck with a high resolution multibeam echo sounder, which is capable of mapping the sea floor down to 500 metres.

The team will also operate the sea mapping floor equipment on the national research ship RV Investigator.

Mr Edwards said it took about an hour to map the shipwreck.

‘‘MV Lake Illawarra was a 135-metre long bulk carrier, which is currently lying in 34 metres of water on the southern side of the Tasman Bridge,’’ he said.

‘‘Only 12 per cent of Australia’s ocean floor has been mapped, which means every day I head out to sea, I find new things, things that no one else has ever seen before and that’s pretty cool.’’

The echo sounder can be lifted by a single person and fits onto any vessel.

It works by generating a fan-shaped acoustic beam into the water that collects and sends information and data at a rate of 50 times a second.