The B class of submarine was intended for coastal patrol work. The boats had petrol engines for surface propulsion and batteries for underwater propulsion. The design was intended to overcome the limitations of speed, endurance and seakeeping that affected the boats of the previous A class, and the boats were substantially longer and heavier.
Improvements were made to surface speed, about 12 knots and endurance (1,300 nautical miles), but the underwater speed of 7 knots (13 km/h) was much the same as the A class. Seakeeping was improved by the addition of a deck casing, and underwater manoeuvrability by the addition of hydroplanes.
| Displacement | 287 tons surfaced; 316 tons submerged |
| Length | 135 ft |
| Beam | 13.5 ft |
| Speed | 12 knots (22 km/h) surfaced, 7 knots (13 km/h) submerged |
| Range | 1,300 nautical miles (2400 km) at 8 knots (15 km/h) on the surface |
| Complement | 15 |
| Armament | 2 × 18 in (457 mm) bow torpedo tubes |
In the early hours of 4 October 1912 HMS B2 was on the surface about four miles north east of Dover when the 23,000-ton steamer SS Amerika, on passage from Hamburg to New York, via Southampton, collided with the submarine. B2 was struck just forward of the conning tower: – a fatal blow that sent the submarine immediately to the bottom.
Diving: The sub is in a depth of 33m on a mixed bed of sand and chalk. Until recently this small submarine has had her bow buried into the seabed, however the whole of the sub is currently exposed from her distinctive bluntly curved bow to the prop covered in anemonies. The conning tower is still in place with its hatch open.
