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 going with the use of scuba in the mid-20th century) has branched off into a number of subdisciplines that look at everything from how humans interact with water to the search for airplanes that make water their final resting place. And plenty of above-ground archaeologists eventually find themselves looking to nearby bodies of water for answers.

Finding An Ancient Spanish Shipwreck Led by clues found in old documents, maritime archaeologist Robert Grenier makes a thrilling discovery.

Challenging discipline

Often, the hunt for underwater objects presents serious logistical and interpretive questions. It can be expensive to look underwater at all, and researchers must recruit divers (who are often also archaeologists) with the ability to document and handle delicate objects appropriately. Weather conditions and tides can stymie an expedition.

View Images This illustration shows a remotely operated submersible used in underwater research. Illustration by Richard Schlecht, Nat Geo Image Collection

And once a site is located, it can be tricky to study. Water is dynamic, and objects are susceptible to its ebb and flow. It can break up materials and jumble them in a way that makes interpretation difficult. Conservation can be even trickier; water can be hard on already delicate objects, and moving a newly recovered object is even harder when it’s underwater.

Luckily, archaeologists have plenty of technology to combat those challenges. LiDAR can reveal structures and objects underwater and map sites; sonar, magnetometors, and other remote sensing devices can help, too. Advanced photography and videography can bring sites to life even for those who’ll never venture into the water. And a new generation of submersibles is driving new discoveries. The R/V Petrel, for example, carries two onboard robots that have helped uncover 21 World War II vessels, including the U.S.S. Indianapolis.

View Images Octavio del Rio examines a skull from a funerary deposit in northern Yucatan, Mexico. Photograph by Wes C. Skiles, Nat Geo Image Collection

Helping hands

Underwater archaeology also depends on good relationships with other communities familiar with the bodies of water they work in. That became clear to researchers who were alerted to a large cache of shipwrecks near Fourni, Greece, by a local fisher. The assistance of the area’s fishers ended up helping archaeologists discover 23 shipwrecks in the area in 22 days. Volunteers can drive much of the field, as in Florida, where volunteers work alongside archaeologists.

Local and international laws also apply: UNESCO, the UN’s cultural arm, has established international law around underwater cultural heritage that mandates in situ (“in place”) preservation as the ideal option when researching a submerged archaeological site. That means many underwater finds must be left where they were found.