Sjöormen-class submarine

The Sjöormen class (Sea serpent) was a class of submarines built for the Swedish Navy in the late 1960s. They had a teardrop hull shape and were capable of diving to 150 metres (490 ft). At the time of their deployment they were regarded as one of the most advanced non-nuclear submarine-classes in the world, incorporating many new features including x-rudder and anechoic tiles. Both speed and underwater endurance was at this time very high for a conventional submarine. The submarines were retired by Sweden in the early 1990s. In the late 1990s, all five submarines were acquired by the Republic of Singapore Navy (RSN) and four were relaunched as the Challenger class following modernisation and tropicalisation. The fifth was never relaunched as it was used for spare parts and subsequently scrapped in the 2000’s. As of November 2024, the Challenger-Class has been decommissioned.