This April 6, 2005 file photo shows a coral reef and fish on a snorkeling trail off Buck Island near St. Croix, U.S. Virgin Islands. U.S. scientists on Tuesday, April 7, 2015 completed a nearly two-week mission to explore waters around the U.S. Virgin Islands as part of a 12-year project to map the Caribbean sea floor and help protect its reefs. (AP Photo/Brent Hoffman, File)

U.S. scientists on Tuesday completed a nearly two-week mission to explore waters around the U.S. Virgin Islands as part of a 12-year project to map the Caribbean seafloor and help protect its reefs.

A team with the National Oceanic and Atmospheric Administration studied an area of 270 square miles (700 square kilometers), using equipment including underwater gliders and a remotely operated vehicle to help map the seafloor and locate areas where fish spawn. They focused mostly on the southern coast of St. Croix and…