Obviously, penetrating hits above the waterline are unlikely to cause sinking without fires or other catastrophic damage. But what about the electronics and other internals which are there to allow the ship to fight? Can a hull be turned into swiss-cheese by several .50 cals mounted on RHIBs? What about 30mm cannon on patrol boats? Sure, each 30mm shell would cause little structural damage, but how many data cable bundles, computers, CIC, sailors, etc., would be destroyed by the internal explosion of these relatively small cannon shells? A quick burst of the cannon would dump a dozen or more shells through the hull...if it's not armored or hardened.
I'm curious about modern naval architecture and what level of protection is afforded to warships against guns (and to a lesser extent, to missiles). Any armor is better than none... What do they have?
If you have a copy of the sim. Load a blank scenario in....say using a Freedom Class Littoral ship and then have an opponent side launch an attack with RHIB's or Patrol Boat with a cannon and see what kind of damage is the result of numerous attacks. You can determine yourself if enough damage will cause a " mission kill" by knocking out enough weapons systems or electronics.
Just an idea.
USS Dwight D. Eisenhower (CVN-69) 1990-1994.