Curious about still-hidden archaeological treasures? Just add water—that’s the concept behind the emerging field of underwater archaeology. But don’t be deceived: It’s anything but simple, and recent advances have made it one of the most exciting forms of modern archaeological research.

It’s always been difficult to access sites under water, but there’s a particular allure to potential archaeological sites hidden under oceans, lakes, and rivers. Shipwrecks are far from the only thing to document, study, and preserve underwater: there’s also everything from very ancient human remains to submerged settlements, like portions of ancient Alexandria, the Egyptian city that partially sank into the Mediterranean over the centuries.

Over the years, the relatively recent discipline of underwater archaeology (which really got