Sjöormen class submarine

The "Sjöormen" class were a group of submarines built for the Swedish Navy in the late 1960s. They had a teardrop shape and were capable of diving to 150m. The ships were retired by Sweden in the early 1990s

ale to Singapore

Four of the ships were sold to Singapore in 1996 and modernised in the late 1990's by Kockums. Various modifications were required to suit the boats to tropical waters. A comprehensive tropicalisation programme was carried out for all four submarines, which involved installing air conditioning, marine growth protection systems and corrosion-resistant piping. They are currently (2008) in service with the Republic of Singapore Navy as the "Challenger" class

hips

References

* Conway's All the World's Fighting Ships 1947-1995
* [http://www.kockums.se/submarines/challenger.html Page from Kockums]