The image of Neanderthals has changed quite a lot in the past few decades thanks to new discoveries. We now know that they may have decorated their bodies, buried their dead and created art. Now, we can add another skill to the list, diving under the ocean for shells that they fashioned into tools, according to a new study.

A group of researchers analyzed clamshells and volcanic rocks from an Italian cave, which showed Neanderthals collected shells and pumice from beaches. Due to specific indicators on some of the shells, the researchers also believe Neanderthals waded and dove into the ocean to retrieve shells, meaning they may have been able to swim.

Only about ten feet above the beach in central Italy’s Latium region, the Grotta dei Moscerini cave was excavated in 1949. Archaeologists recovered 171 clamshells that were modified into sharp tools. They all belonged to a local species called Callista chione, or the smooth clam.

University of Colorado researcher Paolo Villa and colleagues looked at such tools, which had been stored at the Italian Institute of Human Paleontology because the cave itself is no longer accessible. They concluded some must have been gathered from the seafloor by Neanderthals.

“The fact they were exploiting marine resources was something that was known,” said Paola Villa to CNN, study author and curator of the University of Colorado at Boulder’s Museum of Natural History. “But until recently, no one really paid much attention to it.”

Most of the shell tools had abraded surfaces. But nearly a quarter of them had shiny, smooth exteriors, typical of shells picked live from the seafloor. In their study, Villa and her colleagues argued that diving for clams may have been a routine part of Neanderthal life in this region.

The shells were modified to be used as scrapers. These were more efficient than thin flinty rocks, which can’t sustain a sharp edge. It’s possible that stone was hard to come by, which is why they sought out shells. Or perhaps the shells suited their needs better, the researchers said.

The findings align with evidence from a recent study by Prof Erik Trinkaus suggesting that some Neanderthals suffered from “surfer’s ear,” based on bony growths found on the ears belonging to a few Neanderthal skeletons. And previous research has pointed to the fact that Neanderthals engaged in fishing.

The new study “reinforces what is becoming increasingly evident from a variety of different sources of archaeological data: Neanderthals were able to do, and occasionally did, most of these kinds of behaviors that had been considered to be special to modern humans,” said Trinkaus to the Smithsonian Magazine.

Key facts on Neanderthals

Neanderthals are considered the closest extinct human relative. Among the features of their skulls, they had a large middle part of the face, angled cheekbones, and a huge nose for humidifying and warming cold air. They also had shorter and stockier bodies as an adaptation to living in cold environments.

They made and use a diverse set of sophisticated tools, controlled fire, lived in shelters, made and wore clothing, were skilled hunters of large animals and also ate plant foods, and occasionally made symbolic or ornamental objects. Evidence has been found of them burring the dead and marking graves with offering as flowers.