Finding cool things is part of the allure of outdoor adventure. For a paleontologist searching a waterway in Virginia, discovering a six-foot, 5 million-year-old baleen whale skull was sort of the ultimate in cool things.

When Jason Osborne first found the six-foot skull in 2013 on a diving trip, he knew dealing with the weight and potential fragile nature of the fossil would be a real challenge.

As a result, he was not able to retrieve it until now. After finding sponsors and enlisting the help of a team of experienced excavators, they also deployed floating body bags. The bags were used to trap any sediment that may fall off while lifting the skull, which weighs between 300 and 500 pounds; clearly not something he could just pull up and throw in his pick-up truck.

Osborne had been exploring geological formations underwater when he literally bumped into the bone.

 “I might have actually banged my head into it,” he told National Geographic. “I spent probably 20 minutes or so around the skull to kind of determine size, what I’d have to deal with, how would get this to the surface,” Osborne says. “At the time I was like this is going to be impossible to try to recover, as massive as it is.”

Once retrieved, experts determined that the skull belonged to an extinct species of baleen whale, which likely died 5 million years ago. The presence of such a large and old creature in an inland waterway in the American South seems outlandish and confusing, unless we consider the greater geography of the region in prehistory.

Most of the Atlantic Coast was not coastline millions of years ago. In fact, where the Potomac River now runs was once an ancient whale calving ground. The entire region is full of fossils, making it a wonderland for paleontologists like Osborne. And not too far away, a team of researchers from Culvert Marine Museum dug up another whale skull in July. That one was estimated to be an astounding 15 million years old.