During the construction stage of an offshore wind farm, a substation platform or a cable route, the construction site needs to be secured by a guard vessel. The vessel must constantly monitor marine traffic near the construction site visually and with radar and AIS. When an external vessel approaches the construction site, measures are to be taken to secure the construction site and vehicles, and the external vessel must receive information on how to safely get past the site. The technological and manpower requirements for the vessel are stipulated in the BSH approval notification for the construction site, depending on the task, deployment area and traffic volume. A guard vessel’s essential features include being able to stay offshore for long periods of time (up to 30 days and longer) and great seaworthiness combined with high service speeds.