A spate of shipwrecks recently found near a group of Greek islands has given researchers new insights into how trade routes and sailing technology evolved in the Eastern Mediterranean. And with more exploration planned, additional discoveries are still likely.

Over a stretch of two weeks in September, tips from local fishermen and sponge divers led a team of Greek and American archaeologists to the precise locations of 22 shipwrecks in a 17-square-mile area around the Fourni archipelago in the eastern Aegean.

The find is remarkable both for the sheer number of wrecks in the small area and the range of time periods the vessels came from.

The earliest wreck dates to the Archaic Period (700-480 B.C.), while the most recent is from the Late Medieval Period (16th century A.D.). Ships from the Classical Period (480-323 B.C.) and the Hellenistic Period (323-31 B.C.) were also found, though a majority—12 of the 22—sailed and sank at some point during the Late Roman Period (300-600 A.D.)

“It’s an extremely rich area,” says Greek director George Koutsouflakis, an archaeologist with the Hellenic Ephorate of Underwater Antiquities.

Finding 22 shipwrecks in only two weeks is incredibly rare, but more discoveries in the area are likely—the team has surveyed only 5 percent of Fourni’s coasts, and local fishermen have given them many more tips.

All the ships were merchant vessels traversing a route that connected Anatolia, Samos, and the Black Sea region to Rhodes, Cyprus, and even Egypt. Wooden ships generally decompose underwater or get eaten by seaworms. But their cargo—ancient clay storage jars called amphorae—survive. Each ship was carrying several hundred amphorae. By assessing the size and shape of the jars, archaeologists can infer where and when they were made.

Residue or DNA analysis will confirm what they contained, but the primary goods are not in doubt.

“We know from comparable shipwrecks and terrestrial sites that the three major goods would have been olive oil, wine, and fish sauce,” says Jeffrey Royal, a co-director from the Florida-based RPM Nautical Foundation.

These bulk items were likely stored in the larger amphorae, while smaller ones might have held jams, fruits, honey, hazelnuts, almonds, as well as luxury commodities like perfumes.

Many merchant crews in the Classical Period were composed of 10 to 15 sailors. By the Late Roman Period advances in sailing technology, such as lateen sails that ran from fore to aft, reduced crews to as few as five to seven people. Unlike the famous Greek and Roman warships known as triremes, the smaller merchant ships derived power primarily from sails rather than banks of rowers.

Some of the ships around Fourni appear to have encountered sudden storms and strong winds that smashed them against cliffs and rock formations in shallow water.

“You can look at the spatial patterning of the sites and reconstruct a plausible story about what happened,” says Peter Campbell, a co-director of the project from the University of Southampton. “It looks like some of them were anchored behind cliffs to shelter from a northwest wind, but this made them vulnerable to a southern wind that drove them against the cliffs.”

The ancient sailors’ chances of survival would have been slight. “Of the 22 wrecks we studied, there were probably four where they might have had a chance to swim to a beach or shore. But most of the spots were next to sheer cliffs. There’s no way they would’ve survived in a storm,” Campbell says.

The archaeologists have only begun to analyze the material they collected from the shipwrecks in September, but the abundance of late Roman ships is already striking. They suspect that this apparent spike in traffic may be linked to the rise of Constantinople and the Eastern Roman Empire in the fourth century. They expect their ongoing research to answer many specific questions about ancient maritime trade networks and how they related to the shifting political structures of the Eastern Mediterranean.

Fourni was already known to some smugglers before this September’s survey. Locals had reported seeing suspicious activity in the water near certain sites, and the archaeologists found some evidence of looting when they dove the wrecks.

Pinpointing exact locations for 22 of the area’s shipwrecks will make it easier for Greek authorities to supervise the sites. The archaeologists also hope that the knowledge gained during excavations will give local communities a stronger sense of connection to their history.