7.13.3 Rescuing Survivors - according to this rule it is possible to rescue 100% of the crew of a sinking ship.
But presumably it is sinking because it has been hammered by the opposition and there has already been casualties.
Highly unlikely that ALL the crew are available for rescue!!.
The rule applies to rescue from sinking or sunk ships due to all causes. So it is not unlikely, in certain circumstances, for all the crew to be rescued. A example of such a case was the loss of HMS Audacious to a mine. Her entire crew was rescued (in fact, only 1 fatality occurred during the attempt to save her and that was an unfortunate seaman from HMS Liverpool who was struck by a piece of armor plate when Audacious capsized and blew up). For actions under gunfire, you may want to adjust the roll as you feel appropriate.