From Netherlands Defense Ministry: The Royal Netherlands Navy has a torpedo training ship, HNLMS Mercuur, which accompanies submarines on exercise. It serves as a sailing maintenance shed for torpedoes and as a target ship for submarines to fire dummy torpedoes under.
Specifications
Displacement: 1,400 tonnes
Length: 64.8 meters Beam: 12 meters
Draught: 4.3 meters Speed: 14 knots
Propulsion: 2 x MAN 6L-20/27 diesels (1,632 hp total)
Ship's company: 39
Armament: 1 underwater launch tube for Mk. 48 torpedoes