A submarine damaged on the surface faces a special dilemma because unseen pressure-hull damage can make the next dive fatal. If it remains surfaced far from home, aircraft and surface forces can find it much more easily. A damaged boat might therefore be more operationally useful to the defender than one sunk immediately. The Kriegsmarine could send other submarines, aircraft, motor torpedo boats, or destroyers to escort it, multiplying the diversion created by the original attack. This was a later-war consequence rather than a fully worked-out interwar plan, but it clarifies why anti-submarine success cannot be reduced to sinkings alone.
Notable Point · 15:07-17:07
A damaged U-boat can divert more forces than a sinking
Damage that prevents a submarine from diving can force it home and draw aircraft, boats, destroyers, or other U-boats away from their own missions to protect it.