Scientists have new clue to mystery of sunken sub

It's long been a mystery why the H.L. Hunley never returned after becoming the first submarine in history to sink an enemy warship in 1864, but new research announced Friday may lend credence to one of the theories. Scientists found the eight-man crew of the hand-cranked Confederate submarine had not set the pump to remove water from the crew compartment, which might indicate it was not being flooded.

That could mean crew members suffocated as they used up air, perhaps while waiting for the tide to turn and the current to help take them back to land.

The new evidence disputes the notion that the Hunley was damaged and took on water after ramming a spar with a charge of black powder into the Union blockade ship Housatonic.