The Navy is responsible for continuous surveillance and defence at sea, in coastal areas and in the archipelago. It has a high peacetime readiness and defence capability.

The maritime defence system carries out surveillance in Finnish territorial waters, repels attacks at sea and protects important shipping lanes and maritime traffic.

Coastal units, based on coastal artillery strength, carry the main responsibility for defence of Finland's coastal areas and the archipelago. Naval task forces and mobile coastal forces form the mobile maritime defence force, and are supported by units of the Air Force.

Even in peacetime, coastal forts located in the most critical areas are kept in readiness to fire warning or defensive shots.

The comprehensive situation data provided by the command and control systems of the Navy and the Coastal Artillery enable well-coordinated command of troops and forward observation.

The sea surveillance data system uses data generated by surveillance equipment and systems to form a comprehensive database of actively monitored targets. There may be as many as several hundred targets under simultaneous surveillance.

The Coastal Artillery carries out continuous radar, ground and underwater observation. The fixed surveillance stations of the Defence Forces and the Frontier Guard are the backbone of the surveillance system. Vessels also carry out surveillance and guard duties.

The capacity to repel attacks at sea and in the archipelago is based mainly on obstacles and the missile and artillery systems of the Coast Artillery.