Never-before-seen photos reveal WWI-era submarine 1,300 feet before surface where 19 sailors perished in 1917

In Dec. 1917, 19 sailors serving on a World War I-era U.S. submarine made the ultimate sacrifice during a training mission. 

Perhaps fittingly, scientists have captured never-before-seen photos of its watery resting place off the California coast just ahead of Memorial Day.

The U.S. Navy submarine, USS F-1, went down after a collision with its sister ship on Dec. 17, 1917, and now sits 1,300 feet below the surface on the ocean floor off San Diego. 

MYSTERIOUS 18TH-CENTURY WARSHIP...