eli5: I was just reading about modern submarines on Wikipedia such as the German type 212. Why are they capable of travelling faster submerged than surfaced?

Question

I would have thought that the opposite was the case as less mass is pushing against the water while surfaced.

In: Physics

Answer 1

Once you get down in depth even a short distance, the propeller gets a better bite on the water. On the surface, the top 10% of the propeller might still be underwater, but it is just making a lot of turbulence.