NMS Marsuinul (The Porpoise) was a submarine of the Romanian Navy, one of the few warships built in Romania during the Second World War. She was laid down at the Galați shipyard in 1938, launched in 1941 and completed in 1942. She had a crew of 45, a displacement of 636 tons on surface and 860 tons in immersion, a length of 68.7 meters, a beam of 6.5 meters and a draught of 3.6 meters. Her top speed was of 16 knots on surface and 8 knots in immersion and had a range of 8,000 nautical miles. Her armament consisted of 1 x 88 mm SK C/35 naval gun in the front and 1 x 20 mm Oerlikon autocannon in the rear, as well as 6 x 533 mm torpedo tubes.