German U-3008 XXI Electro Boat, same as the U-2015 submarine used by Clive in Atlantis Found.

According to Uboat.net, 118 XXI submarines were commissioned during WWII and the XXI was the first real combat submarine built to attack from the deep and not to only use submerging as a means to elude threats and detection. This model of U-boat featured several key things that differed from other submarines at the time, including, showers, a large freezer, and the capability to run quieter than others.
But the most striking feature with the XXI was its hydraulic torpedo reloading system that allowed the crew to load all six torpedo tubes in about ten minutes; which was less time that it took to reload one torpedo in its predecessor the VIIC. The XXI also carried three times the electrical power of the VIIC.
Technical information for type XXI
Displacement:
(tons) 1621 (sf)
1819 (sm)
2100 (total)
Length: (m) 76,70 oa
60,50 ph
Beam: (m) 8,00 oa
5,30 ph
Draught: (draft) 6,32 m
Height: 11,30 m
Power: (hp) 4000 (sf)
4400 (sm)
Speed:
(knots) 15,6 (sf)
17,2 (sm)
Range:
(miles / knots) 15500/10 (sf)
340/5 (sm)
Torpedoes: 23
6/0 (bow / stern tubes)
Mines: 12 TMC
Deck gun: No deck gun
Crew: 57-60 men
Max depth: ca. 280 m
(919 feet)
sm = submerged, sf = surfaced, ph = pressure hull,
oa = overall, hp = horsepower.
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