In the marine sciences, exploring diversity represents a major challenge, as only 10% of marine species are known and only around 100 high-quality genomes of marine organisms have been made available to the scientific community. The ATLASea programme1 (PEPR Exploratoire 2023-2030, led by CNRS and CEA) proposes to decipher and exploit the colossal wealth of information from marine biodiversity along the French coast. 4500 marine species will be sampled by the DIVE-Sea Targeted Project led by MNHN, with a high coverage of species from mainland France, but also including species from overseas territories. The samples will be entrusted to the SEQ-Sea Targeted Project led by CEA to produce genome assemblies associated with high-quality structural annotations. The BYTE-Sea2 Targeted Project will centralise all the genomic data produced by the ATLASea project into a single web portal3 and integrate the genomes of related organisms sequenced by other consortia. It will guarantee the interoperability and security of the data, and facilitate its dissemination and use in accordance with the FAIR and Open Science principles. The environment developed will provide access to sequencing data on the genomes of marine organisms, including information on the genomic sequence, genes and coding and non-coding regions, and will offer advanced tools for genome analysis, genome comparison and data visualisation. The portal will also be used by the scientific community to track the progress of the project. By providing access to this large mass of information on marine species, the ATLASea programme will help to understand, study and preserve a broad diversity of marine life forms.