This paper presents the creation of a thesaurus in the Maritime Heritage (MH) field. The suggested controlled vocabulary could improve methods for archiving oral sources, written accounts, imagery, 3D archeology, and other multimedia objects related to people and periods from ancient times to recent history. It has been created to cover the indexing needs for resources from Greek Maritime Galleries, Libraries, Archives and Museums (GLAM) institutions hosted in a MH platform of the research infrastructure Intelligent Research Infrastructure for Shipping, Supply chain, Transport and Logistics (EN.I.R.I.S.S.T.). Its terms are derived from the collections pertinent to maritime activities. Although the construction of this vocabulary took into consideration specific data and their documentation, the goal is to go beyond ΕΝ.Ι.R.I.S.S.T. to assist MH documentation projects and professionals/researchers in organising and archiving MH data. The long-term ambition is to leave an imprint in improving MH data communication in general and contribute to promoting MH as a separate Cultural Heritage (CH) branch. The methodological approach was sensitive to the history of the artefacts, the shipping history and terminology, CH and general vocabularies, as well as the pre-existing practices. Terms and subject headings already existing in the vocabularies of reference were leveraged. The rules and standards of thematic indexing, monolingual and multilingual thesauri creation, and terminology standards were followed.