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The divers descended 410 feet into the Mediterranean off Italy, shining bright lights on a ship that sank thousands of years ago. A sea-crusted anchor rested amid piles of terra cotta jars traditionally used to carry wine, olive oil and other cargo.

Some of the world's most advanced divers with a Florida-based group called Global Underwater Explorers are helping Italian researchers unlock a shipwreck mystery dating to the second Punic Wars between Rome and Carthage. Trained to descend farther than most divers can go, they helped archaeologists earlier this year by fetching artifacts with their hands and floating them to the surface.

"It felt very much like a ghost ship awaiting the boarding of ancient mariners," said Jarrod Jablonski, one of the divers.