The Type I U-boat was a 1936 attempt by the Kriegsmarine to produce an oceangoing U-boat. Only two were produced (U-25 and U-26 ) by AG Weser of Bremen, having been found to have poor stability, slow dive rate, poor maneuverability under water, and mechanical unreliability.
However, both boats produced a number of successes in the early months of the Second World War. U-25 sank eight ships and damaged one; U-26 sank 11 and damaged two. U-25 struck a British mine in the North Sea on August 1, 1940. All hands were lost.
U-26 was scuttled on July 1, 1940, having been rendered unable to dive by depth charges from the British Corvette HMS Gladiolus and an Australian Sunderland flying boat. The entire crew was eventually saved.

General Characteristics

Displacement: 862 tons (surfaced); 920 tons (submerged)
Length: 237.5 ft (72.39 m)
Beam: 20.4 ft (6.21 m)
Draft: 14.1 ft (4.3 m)
Surface Propulsion: 2 MAN 8-Cylinder diesal motors; maximum performance 3,080 shp = 18.6 knots
Underwater Propulsion: 2 BBC electric motors; maximum performance 1,060 ehp = 8.3 knots
Batteries: Two 62-cell (9,620 amp-hours)
Armament: One 105-mm deck gun, 1 20-mm anti-aircraft gun, six 533-mm torpedo tubes (four bow, two stern), 14 torpedoes or 28 TMA mines
Crew: 44-46
Maximum diving depth: 656 feet (200 m)