Beyond the sea walls: Underwater archaeology reveals the hidden scale of ancient Mediterranean ports

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility: Looking beyond sea walls substantially changes harbor capacity estimates of ancient Mediterranean ports. Credit: Antiquity (2026). DOI: 10.15184/aqy.2026.10424 Trade routes and ports have shaped the history of human civilization, with the Mediterranean network among the most prominent and influential. Yet our understanding of its past is shaped largely by what remains visible on land rather than by the sea itself. Stone-built structures such as docks, quays and breakwaters give us important clues, but they do not always reveal the full picture. To get a fresh perspective from under the sea, researchers launched SHIPs (2023–2028), a multiyear underwater archaeology project combining hands-on fieldwork across the Mediterranean and a major freshwater lake. By approaching harbors from the water rather than the shore, the project maps the different elements of a port system and examines how they worked together. They discovered that anchoring areas beyond the formal stone walls played a decisive role in how much traffic a port could handle. Judging a port's capacity by its surviving stone docks alone overlooks the many ships accommodated beyond them. Ships anchored in sheltered natural bays, were beached along open coastlines or moored in deeper waters beyond the harbor walls. These practices reshaped how researchers view harbor capacity in the ancient harbors of Caesarea, Terracina and Port-Vendres. The findings are published in Antiquity. Archaeology under the sea Archaeologists have long struggled to compare ports fairly, since there's never been a standard way to measure trade capacity across such different environments. Counting only the formal harbor basin badly underestimates how many ships a port could actually handle. The SHIPs project instead treats ports as complete working systems viewed from the sea, and the team built a standardized, four-part framework to study them properly. The first component was mooring techniques, which researchers approached in a new way by combining physical evidence with historical records to understand how ancient ships anchored and docked. They examined surviving ropes, mooring rings and stone docking posts, then compared them with 19th-century photographs of sailing vessels. The photographs revealed how ships were physically arranged at dock and helped test the strength of ancient harbor structures. The second component was drafts and depths. To determine whether a port could handle large trading ships, the team reconstructed how deep the water once was. Researchers drilled geological core samples, searching for ancient clay layers that mark the original harbor floor, then compared that depth with the draft of ancient merchant ships to see which vessels could fit. Port-Vendres: locations of shipwrecks and assemblages. Credit: M. Salvat/Association pour les Recherches Sous-Marines en Roussillon 2016. They then mapped the shape of the coast and ports using lidar (aerial laser scanning) for broad, initial surveys of the landscape, finding walls and structures buried under the soil without digging them up. Alongside this, they reviewed old archives, historical photographs and property maps. For areas of the harbor that are completely underwater, they use specialized boats to scan the seabed with side-scan sonar, sub-bottom profilers that scan beneath the mud and metal detectors to locate ancient shipwrecks and scattered cargo. Underwater investigators managed to pin down where the Port-Vendres 5 wreck rests, only to discover that little of it has survived intact. Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. Sign up for our free newsletter and get updates on breakthroughs, innovations, and research that matter—daily or weekly. Their findings showed that the harboring capacity and layout of Caesarea in Israel and Port-Vendres in France extended far beyond what was traditionally believed. At Terracina in Italy, evidence pointed to soil and mud gradually building up over time and reshaping the anchoring areas, challenging older, fixed reconstructions of what ancient port landscapes once looked like. Tiberias: the Byzantine jetty during the 2025 excavation, looking east. Credit: E. Nantet. While excavating a jetty in Tiberias, on the Sea of Galilee, researchers found that ancient underwater concrete stayed in use far longer than anyone had assumed. The hub operated well past the early Imperial period, from the late first century BCE to the second century CE, and continued into the Byzantine era. Better mapping can help protect fragile underwater heritage, including shipwreck sites, and help heritage authorities build more accurate reconstructions of ancient trading ports. Written for you by our author Sanjukta Mondal, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you. Publication details Emmanuel Nantet et al, Beyond the mole: Redefining harbour capacity for the ancient Mediterranean, Antiquity (2026). DOI: 10.15184/aqy.2026.10424 Journal information: Antiquity © 2026 Science X Network