Heracleion-Thonis — the Greco-Egyptian port city under six metres of Mediterranean.
Heracleion (in Greek) — Thonis (in Egyptian) — was the principal port of trade between the eastern Mediterranean and Egypt from the seventh century BCE until the foundation of Alexandria in 331 BCE diverted the trade westward. The city continued in reduced form through Roman and early Byzantine periods before sinking into the Mediterranean between the second and eighth centuries through a combination of sea-level rise, soil liquefaction during seismic events and the steady subsidence of the Canopic-mouth delta. Rediscovered by Franck Goddio's team in 2000, the site is the journal's primary documented dive location. Tarek Ramadan is the lead editor.
The site's structural picture.
The submerged city sits between four and seven metres below the current Mediterranean sea level in Abu Qir Bay, approximately six and a half kilometres off the modern Egyptian coast at the village of Aboukir. The site covers approximately eleven square kilometres in total, of which roughly fifteen percent has been excavated to professional archaeological standards by the institutional expeditions; the remainder is documented by remote-sensing geophysical survey and by the journal's own visual dive-log observations. The seabed silt is unusually deep — a soft layer of fine silt three to seven metres thick over the original Ptolemaic-era ground surface — which has preserved organic and metallic material remarkably well but which also makes excavation slow and visibility a recurring challenge.
The five documented survey grids.
The institutional expeditions have divided the site into five named survey grids, and the journal's field reports follow the same grid structure to keep the documentation aligned with the institutional record. Grid A — the temple of Khonsu-Herishef. The principal temple complex, at the centre of the city's surviving footprint. Major structural finds include the two black granodiorite statues of an unidentified Ptolemaic queen and her royal consort, the surviving pylon foundations, and a complete set of foundation deposit stelae bearing the city's name in both Greek and demotic Egyptian. Grid B — the southern harbour. The basin where the trading vessels moored; surface finds include anchor stones, jar fragments, lead-sheathed timber and three documented small-vessel wreckage sites. Grid C — the residential quarter. The dense residential area east of the temple, with surviving wall stubs of approximately thirty-eight identifiable building footprints. Grid D — the eastern necropolis. A small necropolis with seventeen documented burials, mostly Ptolemaic-period inhumations in stone-lined chambers. Grid E — the canal-mouth approach. The northern approach where the Canopic branch of the Nile met the Mediterranean; a transitional area between river-borne and sea-going trade with characteristic mixed material.
The journal's contribution by grid.
The journal's one hundred and forty-eight field reports across ten dive seasons are distributed unevenly across the five grids. Grid A (temple) has received fifty-three reports — the institutional teams have allowed our alongside-dives most regularly here because the temple area is the season's typical opening dive. Grid B (southern harbour) has received forty-one reports, mostly during the spring season when the underwater visibility is best. Grid C (residential) has received twenty-eight reports; the visibility in the residential area is structurally poorer because the silt sits looser. Grid D (necropolis) has only sixteen reports because the institutional teams restrict alongside-diving on necropolis material to avoid disturbance. Grid E (canal mouth) has ten reports, mostly transitional dives between grids.
The Goddio Foundation expeditions and our alongside-diving.
The European Institute for Underwater Archaeology — under Franck Goddio's directorship — has been the primary excavator at Heracleion-Thonis since the 2000 rediscovery. The institutional dive seasons typically run spring and autumn, with twelve to eighteen weeks of dive operations per year. The journal has logged alongside-dives with the Goddio team on three documented occasions: spring 2018 (six alongside-dives in Grid A, written consent from the foundation), autumn 2020 (eleven alongside-dives across Grids A, B and E during the foundation's twentieth-anniversary documentation work), and spring 2024 (eight alongside-dives in Grid B for the harbour-anchor cataloguing project). All alongside-reports were reviewed by the foundation's dive coordinator before publication and carry the foundation's name in the published reports. Our own independent dives at the site use a separate dive-charter permit and operate on days when the institutional teams are not at the site, with the institutional teams' awareness of our schedule.
What we do not publish.
The journal does not publish new finds from the institutional expeditions before the institutional teams publish them. We do not publish location coordinates precise enough to enable independent diving. We do not publish material from the institutional archive that has not yet been institutionally released — even where we have seen it during alongside-dives, our reports cover only material the institutional teams have already published. The institutional expeditions' academic publications remain the canonical source for new material; the journal complements that record with real-time field observations from the surface and the seabed.
The companion file on the Pharos lighthouse blocks covers the parallel eastern harbour work; the Canopus file covers the related Canopic mouth complex. The journal's methodology sets out the alongside-dive protocol in detail. The 2025 season summary includes the Heracleion-Thonis field season's findings.