Thetis-class gunboat
The "Thetis"-class gunboats was a class of five naval ships of the Hellenic Navy, originally developed for the German Navy as "Class 420" and first commissioned in 1961. Design. Similar in size to corvettes, all five "Class 420"/"Thetis"-class vessels were built by Rolandwerft, Bremen. Although they were designed, built, and designated as "Subchasers" () by the German Navy, subchasers became obsolete after the Second World War due to being unable to keep pace with advancements in submarine technology. Because the ships were designed to chase more modern submarines, they are more commonly referred to as gunboats. The main  armament of "Thetis"-class ships consisted of 20 mm and 40 mm guns, Mk 46 Mod5 torpedoes and mines and anti-submarine (A/S) mortars. The ships were also equipped with sonar. Later the A/S mortars were replaced by a second 40 mm gun and the single torpedo tubes by triple mountings. Upgrades started in 2000 may have included enclosed 40 mm gun mountings and Rheinmetall 20 mm guns to replace the MGs. The last two ships of the class were decommissioned on 22 April 2010.