Maximum speed of traditional ship type

If the submarine is fighting, it is fast in the water and slow in the water.

Submarines will not float to the surface in World War II. At that time, submarines were all diesel-electric submarines, and they had to float and charge. Change the air. If you want to surface. The submarine must be dead. Come up and charge. But when the submarine is charging, the speed is very low, much lower than in the water. Therefore, in combat, submarines are fast in water and slow in water.