Builder Germania Werft (Kiel)
Displacement 786/954 tons
Length 65.2 meters (213 feet 11 inches)
Beam 6.4 meters (20 feet 9 inches)
Draft 3.8 meters (12 feet 5 inches)
Machinery twin shaft M.A.N. 6 cyl 4 stroke diesels and two SSW electric motors
Power (diesel) 2,400 bhp and (electric) 1,200 ehp
Speed (diesel) 17.1 knots and (electric) 9.1 knots
Fuel 115 tons
Radius (diesels) 9,000 miles @ 8 knots and (electric) 55 miles @ 5 knots
Tubes (fwd) two 50cm (19.7 inch) and (aft) two 50cm (19.7 inch) (carried 7 torpedoes)
Guns single 10.5cm/45 cal
AA Guns single 8.8cm/30 cal
Depth of dive .53 meters (160 feet)
Crew 36 men

O-1 (ex U-125; O-2 (ex U-46) and O-3 (ex U-55)

These medium-sized submarines belonged to MS TYPE which was mass produced during the war. Their M.A.N. diesels were extremely reliable. Their surface speed was low compared with Japanese boats, but their radius of operation was much greater. The sturdiness of their construction and the ease of operation made them really a superior weapon. U-46 and U-55 both sank ships in the war (WW I). U-55 sank the Japanese ship TAKI MARU.

In 1926 while being towed from Yokosuka to Kure, O-2 broke the towline and was lost. It was found later by an American merchantman west of Honolulu, and was scuttled on the scene.

These boats exerted a very strong influence on the design of later Japanese submarines.