Inspection and monitoring of marine facilities (eg ports, fish farms, wind farms) both above and below sea surface are an integral part of the facilities´ operations, and the focus on safety means that the need is increasing. However, working at sea near fixed objects entails great risks for personnel and therefore becomes expensive and weather-sensitive. With the Port of Gothenburg as the most important need owner, the Seacat project will complete a surface-going drone, which can perform inspections both above and below the surface in all weathers.