(CNN) If you think Charleston, South Carolina, has plenty of history within its pre-Colonial grounds, just look at what's been hiding 160 miles off the city's coast for thousands of years: a giant deep-sea coral reef system. The chief scientist who helped make the discovery called it unbelievable.

How the hidden reef came to light

Little is known about the natural resources of the deep ocean off the United States' Southeast coast from Virginia to Georgia, so Deep Search 2018 was created to learn more by exploring the deep sea ecosystems. The project, consisting of scientists from the National Oceanic and Atmospheric Administration, the Bureau of Ocean Energy Management, and the US Geological Survey, is nearing the end of its 15-day voyage aboard the research vessel Atlantis.

The R/V Atlantis docked at its home port at the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts.

A pair of dives in a submersible called Alvin confirmed the existence of the coral reef on Thursday, and based on observations, researchers estimate the reef is at least 85 miles long.

"This is a huge feature," expedition chief scientist Dr. Erik Cordes told HuffPost . "It's incredible that it stayed hidden off the US East Coast for so long."

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