A mapping team has made a surprise discovery off Western Australia's north coast, hitting upon a large shipwreck.

Research scientist Miles Parsons said he had watched in shock as the large structure appeared on the sonar screen of the Australian Institute of Marine Science (AIMS) research vessel Solander, while scientists were mapping the ocean floor off the coast of Karratha.

"There was a lot of excitement going on as the object popped up on our screen, and then there were a lot of phone calls going back and forth trying to work out what it was — was it possibly a shipwreck?" Dr Parsons said.

"So we decided we had to go back and have another look and send a towed camera down, and there it was.

"This is the first time I've been involved with finding a shipwreck, and it's incredibly exciting."

The AIMS research vessel Solander, alongside the Broome jetty. ( ABC Kimberley: Erin Parke )

The ship appears to be resting upright 60 metres under the surface, and is 37 metres long and 7 metres wide.

There are no obvious matches in terms of unlocated shipwrecks, and the footage, sonar scans and GPS coordinates have been forwarded to the maritime archaeology division of the WA Museum in an effort to solve the mystery.

The location is being kept a secret because the wreck may end up being listed as a heritage site, and may be the final resting place of people who drowned in the sinking.

More wrecks waiting to be found

The wreck does not appear to be a Dutch sailing boat, like others known to have been wrecked on the Western Australian coast during the 1600s, blown off course from spice trading trips heading to what was then the Dutch East Indies.

Iain Parnum is an expert in underwater acoustics and sonar mapping at Curtin University, who was working on board the Solander when the shipwreck was discovered.

Dr Parnum said at first glance the ship appeared to be a modern design.

"We can see the shape of the boat but it's hard to tell what it could be," he said.

"It could be a work boat, could be a trawler. There are a range of possibilities.

"That's part of the excitement … we don't know what it is, but I'm very keen to find out and I think everyone else is as well."

Research scientist Iain Parnum and marine scientist Miles Parsons are intrigued by the mystery wreck found off the Pilbara coast. ( ABC Kimberley: Ben Collins )

Dr Parnum pointed out that the lack of detailed mapping of Australia's seafloors meant there could be many other undiscovered wrecks sitting underwater.

"Australia has a huge amount of territory underwater and not much of it is mapped … so this does happen," he said.

"You do find unmapped features, particularly in under-surveyed areas like the north-west.

"There are probably lots of other unknown wrecks out there, as we know historically that a lot of ships have gone down along the Australian coast and not all of them have been found."