"Torpedoes were complex even in 1945, and improvements had to be won without losing gains already made. For instance weight and hydrodynamic lift must balance, but adding capabilities often increases weight. So when Tigerfish became heavier than water, it had to be given deployable wings for extra lift whilst running at slow search speeds. However, wings increase noise, and Marconi has designed Spearfish to run with its body at a slight angle to the line of travel. This gives enough lift without wings, even though Spearfish is heavier than Tigerfish."