HMS Dristig, the first patrol boat modified for anti-submarine operations has been delivered to the Swedish Navy in Karlskrona and her crew is being installed on board. The ship will be an important cog for the Navy in the protection of Swedish under water territory. Following the intelligence operation in the Stockholm archipelago in 2014, the need to regain the ability for passive detection of submarines and coastal submarines was identified. Until about 15 years ago, there were four hydrophone buoys that had the task. The Swedish Armed Forces were therefore given the task of adapting six Tapper-class patrol boats to a new mission.
The Swedish Navy was therefore given the mission of adapting six Tapper-class patrol boats by integrating sonar buoys that transmit the sound from its senors to the ship. The sound image can then be analyzed to detect any potential underwater threat. The six vessels are divided between the Third and Fourth Naval Warfare Flotillas with three vessels each. In July 2015 Kongsberg Maritime won a contract to supply new sonar systems as part of a major rebuild and lifetime extension of five vessels in the class conducted by Swede Ship Marine. The Kongsberg Maritime sonar selected for this upgrade is being used for Anti-Submarine Warfare (ASW), Mine and Obstacle detection and Navigation, and is designed for use in shallow water.
The Tapper class are a class of patrol boats in service with the Swedish Navy since the 1990s. Its armament includes 12.7 mm heavy machine guns, anti-submarine Rockets, mines and depth charges. The class was about to retire in 2014 but after the Russian intervention in Ukraine and Russian military build-up in the Baltic sea the boats will now remain and be modified as well. The Tapper boats first function is to protect and patrol the Swedish coastal waters. The ship has been rebuilt and adapted for her new task and among other things, her main engines and auxiliary machines have been replaced. The new ability to receive, listen to and analyze underwater sounds via buoys.