Some 100 million years ago, much of what is now North America was underwater. The body of water scientists call the Western Interior Seaway covered a swath of land that stretched over the entire Midwest. But its secrets have been preserved in countless fossils—and now, over 100,000 of these fossils are being digitized.

Eight institutions are in the midst of a gigantic project to get specimens from the long-lost seaway online. With the help of a $2.1 million grant from the National Science Foundation, they’ll bring fossils out of museums’ drawers and into the public domain with a gigantic digital database that includes photos, 3D models, scans, and classroom curriculum—all free.

The project is ambitious: The NSF award notes that there are an estimated 164,000 samples to digitize. It’s a body of work that will make it easier than ever before to study a period of dramatic evolution that shaped the world we know today. The gigantic sea was filled with creatures like dinosaurs, birds and mollusks, all of which left their fossils behind once the seaway retreated.

Fossils aren’t the only clues the seaway left behind: Chalk deposits made of compacted shells can still be seen in Kansas, and rocks and sediments can still be spotted throughout the Midwest. Scientists think the lost body of water could provide clues about how species ranged and eventually went extinct during the “marine highway"’s heyday—and how the sultry climate of the Late Cretaceous might link to today’s warming world.

But to share their secrets, those fossils have to be available—and to become available, they must be painstakingly scanned and classified. In a press release, the Yale Peabody Museum of Natural History says that it’s digitized about 41,000 specimens in its first year, mostly tiny fragments of bones and shell that have lots to tell about the sea.

Researchers hope to use the finished product to help reconstruct the complex environment of the seaway. But until the difficult project comes to an end, that work will have to wait. Scientists already have an idea of what life was like in the seaway, though. As Bruce Lieberman, senior curator at the University of Kansas’ Natural History Museum, and the primary investigator on the grant, says in a press release, “It’d have been a great place to swim, except there were giant mosasaurs and sharks that would have loved to eat a human.”