Great white sharks have led researchers to discover a secret, hidden oceanic void teeming with life.

Marine biologists began tagging sharks more than a decade ago but the predators' month-long annual pilgrimage to a seemingly barren area in the mid-Pacific region from the coasts of California and Mexico had baffled scientists, the Daily Mail reported.

Now researchers from Stanford University and the Monterey Bay Aquarium, have found that apparently empty stretch of ocean, known as the mid-water, is in fact teeming with life.

A map shows the route of great white sharks from the coasts of California and Hawaii to the void. Image / Supplied
A map shows the route of great white sharks from the coasts of California and Hawaii to the void. Image / Supplied

"The story of the white shark tells you that this area is vitally important in ways we never knew about," Salvador Jorgensen, a research scientist for the Aquarium, told SF Gate. "They are telling us this incredible story about the mid-water, and there is this whole secret life that we need to know about."

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Nicknamed the "shark cafe" by scientists, the water is abundant with squid, jellyfish, deep water fish like bioluminescent lantern fish, and tiny phytoplankton.

The sharks' behaviour also appeared to be determined by gender; with males diving down as many as 140 times a day.

Meanwhile the females would only deep dive, between 426m and 915m during the day, and 200m at night.

They found the sharks were using warm circular currents to get down through to the cold water, suggesting they were following prey.

"Either they are eating something different or this is related in some way to their mating," Jorgensen said.

"It's the largest migration of animals on Earth - a vertical migration that's timed with the light cycle," Jorgensen said. "During the day they go just below where there is light and at night they come up nearer the surface to warmer, more productive waters under the cover of darkness."

The sharks leave the void in the summer and return to coasts.

Sharks swim close to shore off Monomoy National Wildlife Refuge in Chatham, Mass on the US east coast. Photo / AP
Sharks swim close to shore off Monomoy National Wildlife Refuge in Chatham, Mass on the US east coast. Photo / AP

Scientists have been discovering hundreds of new species in such deep water voids in recent years.

And they have been learning more about how animals have adapted to the extreme conditions.

That includes cookiecutter sharks, which have evolved light-emitting organs called photophores, which disguise their shape to prey below making them "invisible".

Scientists say that more research into this mid-water zone could lead to biomedical breakthroughs and give clues about how to tackle climate change.