The Type I U-boat was a 1936 attempt by the German 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 eleven 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 Gladiolus and an Australian Sunderland flying boat. The entire crew was eventually saved.

General characteristics

Displacement: 862 metric 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 diesel motors; maximum performance 3,080 shp (2,300 MW), 18.6 knots (34.4 km/h)
Underwater Propulsion: 2 BBC electric motors; maximum performance 1,060 ehp (790 kw), 8.3 knots (15.4 km/h)
Batteries: Two 62-cell (9,620 ampere-hours)
Armament: One 105-mm deck gun, one 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: 200 m (660 ft)