The waters of the United States’ coast hide oil spill time bombs.

When a ship sinks, it may carry oil with it into the abyss. Storms, corrosion and other events can cause that oil to leak out and contaminate the sea, which kills marine life and poses a health risk to people.

Out of approximately 20,000 shipwrecks in U.S. waters, the National Oceanic and Atmospheric Administration recently identified 36 sunken vessels that most threaten to disgorge their oily innards. NOAA recommended further assessment and potential oil clean-up of seventeen of those shipwrecks. The list was further narrowed to six ships that were most probable to leak 10 percent of their fuel oil or oil cargo. These high risk ships were all off the coasts of New England or Florida.

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NOAA reported their findings to the Coast Guard to guide their efforts in protecting U.S. waters. Besides the risk of pollution from oil fuel and cargo, NOAA’s risk assessment also noted sunken vessels that were grave sites or held historical significance.

The oily wrecks included ships lost to Nazi torpedoes, intense storms, fiery explosions and dramatic collisions. The majority of the risky wrecks (13) were lost during the Battle of the Atlantic in World War II.

ANALYSIS: World War II Shipwrecks Pose Oil Spill Threat

“This report is the most comprehensive assessment to date of the potential oil pollution threats from shipwrecks in U.S. waters,” said Lisa Symons, resource protection coordinator for NOAA’s Office of National Marine Sanctuaries in  a press release. “Now that we have analyzed this data, the Coast Guard will be able to evaluate NOAA’s recommendations and determine the most appropriate response to potential threats.”

IMAGE: An oil tanker torpedoed on May 14, 1942 (National Archives, College Park, MD)