Is 20 knots fast for a submarine in world war 2?
On the surface, twenty knots is a very good speed (maybe a little too good) for a World War 2 sub. Submerged, speed fell off considerably because the hulls were not streamlined as they were after the war. Only Germany toward the end of the war developed submarines with streamlined hulls which made them very fast when underwater. One of them was a small sumbarine which was powered by hydrogen peroxide (rocket fuel) and it could do twenty knots submerged but was extremely dangerous to operate. The other was diesel-electric with a streamlined hull and other improvements which gave it a submerged speed of sixteen knots, a very fast underwater speed for WW2.
