Knowledge about habitats and behaviour of marine animals has become more important following an increased concern that acoustic sources may have an influence on marine life. Databases containing the habitats and behaviour are being filled all over the world. However, at present marine mammal watchers do not have appropriate tools to support the identification and registration of sightings. Therefore, TNO started the development of the Identification & Registration of Marine Animals (IRMA) tool to facilitate this process. This tool interacts with the TNO marine mammal database to retrieve all necessary information for the identification process. Visual and acoustic observations can be entered to obtain a weighted list of possibly observed marine mammals. The internationally accepted Additional Military Layer (AML), containing marine animal information when released, will be used to update this database. All registered information will improve the knowledge about marine animals.