Submarine accidents and German operational risk

Which navy had the worst record for accidental ship losses in World War II?

He points to Germany, mainly because a submarine-heavy force makes accidental losses harder to absorb and more dangerous for the crew.

Force composition changes the consequences of accidents. A surface-ship accident can often be worked around, while a submarine accident quickly becomes dangerous and operationally costly. Germany's submarine-heavy wartime navy was therefore especially exposed to accident losses. The comparison explains more than a simple national ranking would.