The film tells about the work of the specialists of the hydrographic service of the Navy. The specialists serving the Baltic lighthouses monitor the sea, the operation of mechanisms, and aids to navigation equipment that ensures the safety of navigation. Watch of lighthouse specialists on the artificial island of Kolka. View of the rocks of the island of Gogland. Monument to the inventor of radio A.S. Popov. Radio beacon control panel on Gogland Island. Stormy sea view. The crew of the vessel on duty replaces the broken light buoy in its original place.