[lyind]

Why isn't this shape used on submarines already?

[VLM]

On a small ski boat when something like weeds tangles or fouls the prop just pull the lever and tilt the engine out of the water and untangle by hand, including turning the engine on and off its likely a five minute job. Much harder with a submarine in the middle of the ocean.

[simne]

We don't really know, what used on military submarines, because real photos of their props are top secret.

On civ subs, as I know, main driver of choose is just cost, so usually they use conventional cheap designs.