Underwater excavations

The annex to the 2001 Convention sets out the rules for any excavation: a prior scientific project, a qualified archaeologist, a plan for conserving the objects brought up, sufficient funding, complete documentation and publication of results. No object may be sold, exchanged or dispersed.

The project is submitted to the competent authority, which may refuse it if it does not comply with these rules. States must also make sure that foreign teams cooperate with local institutions.

Underwater excavations use suitable methods: sonar survey, photogrammetric recording, gridding of the site, controlled suction of sediment, three-dimensional recording of objects. Divers work in teams, for limited periods, with rigorous safety protocols.

Objects brought up are immediately placed in tanks of fresh or sea water to avoid deterioration. Their treatment — desalination, stabilisation, controlled drying — may take years.

An excavated object is useless if it is not conserved and documented. Each excavation therefore provides for a conservation laboratory, storage space and a treatment budget. Results are published within five years: scientific report, database, exhibition.

Collections are handed to a museum or public institution, which undertakes to conserve them and make them accessible. No collection may be dispersed without the authorisation of the competent authority.

Each supported project includes a training strand: placements for students, training of local diver-archaeologists, conservation workshops. The aim is for States eventually to have the skills needed to carry out and supervise excavations themselves.

In 2024, one hundred and twenty people were trained in this way, half of them in countries that previously had no underwater archaeology team.