From September 29 to October 1, 2025, an underwater archaeological survey was carried out near the archaeological site of Asine, east of Tolo in the Argolid. Thanks to its favorable location, which provides both a natural harbor and an elevated position that contributed to its defensive capacity, this site had already been inhabited since prehistoric times, and showed a continuous habitation until the historic times.

The marine excavation in the area was conducted within the framework of a five-year research program that began in 2022, a collaboration between the Ephorate of Underwater Antiquities, the Swedish Institute at Athens, and Stockholm University, with participants from the University of Gothenburg and the company Nordic Maritime Group. The archaeological investigations of the years 2021–2025 revealed the extent and nature of a large artificial harbor construction, east of the Kastraki site. The main structure consists of a large artificial plateau which lies in shallow waters.

The aim of the 2025 research season was the dating and further investigation of the structures identified on the top of the underwater plateau, in order to determine their function. At first glance, it appears to be a large pile of stones. However, through careful observation of the three-dimensional model of the plateau from 2021 and 2022 and the underwater investigation, stone-built structures can be distinguished, either because of their shape or because they consist of stones of a specific size. For the dating of these structures, it was decided to move stones from three constructions in order to determine whether datable objects existed among them. Nevertheless, the datable finds among the stones were very few. Only two pottery sherds were found. The 2025 research season revealed that the almost square structures on the top of the plateau likely represent different chronological phases and most probably constitute the remains of pier foundations, constructed from wooden caissons filled with stones. After the decay of the wood, what remained are the stones. These presumed caissons are of a later date than the plateau itself.

As had already been pointed out during previous research seasons, the plateauitself, with its clear extension to the west, is considered to belong to the Roman period, based on the amphora fragments found within it. The plateau, with its defined edges, resembles a quay that was originally constructed to stand above sea level. As sea levels rose, the structure submerged. The construction of piers on top of this submerged plateau allowed the harbour to remain in use for loading, unloading, and embarkation.

Further study of the three-dimensional model, in combination with the dating of the material collected during previous research seasons, will form the basis for the future analysis and understanding of this submerged structure and its use in the harbour of Asine.

The results of the research will be published in the scientific journal of the Swedish Institutes in Athens and Rome, Opuscula, and in other scientific journals.