Australian scientists have discovered bizarre prehistoric sea life hundreds of metres below the Great Barrier Reef, in an unprecedented mission to document species under threat from ocean warming.

Ancient sharks, giant oil fish, swarms of crustaceans and a primitive shell-dwelling squid species called the Nautilus were among the astonishing life captured by remote controlled cameras at Osprey Reef.

Lead researcher Justin Marshall Thursday said his team had also found several unidentified fish species, including "prehistoric six-gilled sharks" using special low-light sensitive cameras which were custom designed to trawl the ocean floor, 1,400 metres (4,593 feet) below sea level.

"Some of the creatures that we've seen we were sort of expecting, some of them we weren't expecting, and some of them we haven't identified yet," said Marshall, from the University of Queensland.

"There was a shark that I really wasn't expecting, which was a false cat shark, which has a really odd dorsal fin."

The team used a tuna head on a stick to attract the creatures, which live beyond the reach of sunlight.

Marshall said the research had been made more urgent by recent oil spills affecting the world heritage-listed Great Barrier Reef, and the growing threat to its biodiversity by the warming and acidification of the world's oceans.

"One of the things that we're trying to do by looking at the life in the deep sea is discover what's there in the first place, before we wipe it out," Marshall told AFP.

"We simply do not know what life is down there, and our cameras can now record the behaviour and life in Australia's largest biosphere, the deep sea," he added.

Scientists have already warned that the 345,000-square kilometre (133,000-square mile) attraction is in serious jeopardy, as global warming and chemical runoff threaten to kill marine species and cause disease outbreaks.

Chinese coal ship Shen Neng 1 gouged a three-metre scar in the reef when it ran aground whilst attempting to take a short cut on April 3, leaking tonnes of oil into a famed nature sanctuary and breeding site.

About 200,000 litres of heavy fuel oil spewed into waters south of the reef last March when shipping containers full of fertiliser tumbled off the Hong Kong-flagged Pacific Adventurer during a cyclone, piercing its hull.

It was one of Australia's worst ever oil spills.

Marshall said the cameras would now be sent to the sludge-ridden Gulf of Mexico to monitor the effects of the oil spill there on marine life.