Paleontologist Jason Osborne stumbled upon something unexpected recently, while diving in a Virginia swamp: an enormous whale skull protruding partially from the river bed.

Osborne explained to National Geographic that he literally bumped right into the skull. Though he instantly knew his find was significant, he didn't know how to recover the 500 pound fossil. He started by securing a new boat and diving gear from a local shop, but still couldn't figure out how to get the skull to the surface of the swamp without damaging it.

After consulting with local police officers, Osborne decided to try a novel approach: a body bag. Police body bags are neutrally buoyant and porous, so they drain water while catching any solid residue. It was the first time a body bag had been employed in the service of paleontology, but the plan went off without a hitch.

Osborne immediately brought the skull to Stephen Godfrey, the paleontology curator at the Calvert Marine Museum, who said the skull once belonged to a baleen whale that lived 5 to 6 million years ago, at a time when much of the East Coast of the United States was still underwater. Virginia, Osborne explained, was once a shallow sea, likely used as a calving area for whales. But it wasn't just home to ancient whales; there were predators, too. One of Osborne's most interesting discoveries was a cluster of unhealed lacerations on the skull, which imply the whale was attacked just before death by a massive shark called a megalodon.

Correction: An earlier version of this article stated the skull was found in West Virginia.