Eleven sites were already part of ESONET CA project: connected directly or indirectly to shore, they have been identified and selected for their scientific, technological, and socio economical interests. They were specifically designed to ensure a long term monitoring of chosen critical locations, where the most important biological, chemical or physical processes could be detected or followed up. These observatories are:

Next to these 11 observatories, Koster Fjord observatory has been added for test purposes because of its ease of access, on a shelf.

Moreover, a mobile observatory has been defined to be able to keep track of actions in case of emergency procedures.