For Volvo Ocean racers sprinting from Sydney to Hobart to Auckland (map), sea life means sun and waves and sweat and salt spray. But thousands of feet below them sea life is something altogether otherworldly.

The deep reaches around New Zealand and the Australian island of Tasmania are places of walking lilies, giant spiders, and terrain to rival any national park. Places where mountains remain unnamed, canyons unexplored, creatures undiscovered.

Starting in the 1980s new technologies allowed scientists to finally probe some of the underwater mountains, or seamounts, in this region. They found them to be oases of life supporting a mind-boggling cast of creatures that have changed our understanding of the abyss.

Using an underwater camera and a dredge on various seamounts in three distinct ranges—the Lord Howe Rise and Norfolk Ridge, located northwest of New Zealand, and the South Tasman Rise, just south of Tasmania—the researchers discovered some 850 animal species. That’s hundreds more than had ever been found on seamounts. About a third of them were previously unknown to science.

Perhaps more astonishing, each grouping of seamounts, even those separated by only about 600 miles (970 kilometers), had a unique cast of animals. This shattered the view that the same seafloor creatures could be found throughout vast stretches of the deep ocean.

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