They weren't expecting to find the ancient water, estimated to be 100 to 145 million years old, while boring a hole 1.1 miles (1.8 kilometers) deep into the massive crater, located under the Chesapeake Bay.

The crater was formed about 35 million years ago when a large rock or chunk of ice slammed into what's now the mouth of the bay, off Cape Charles, Virginia, hollowing out a 56-mile-wide (90-kilometer-wide) hole in the floor of the North Atlantic Ocean.

"The water was in the sediment long before the impact occurred. The impact simply reshuffled the sediment in large blocks, which helped preserve it," said study leader Ward Sanford, a hydrologist with the U.S. Geological Survey.

The asteroid wallup also spawned gigantic