How much damage would be done to a swiftboat from a sam would of course depend on size.Before life as a swifty I was a gmm(missles)stryker on Providence clg6.A big part of our effert was conventional gunfire off Nam coast.Use of our missles not allowed,thanks to the experts in DC.They were afraid of Russia and China.
Back to subject.Twice we practiced fired a missle.After it started to move it was out of site in about 2 seconds,awesome.Paint on blkhd,launcher and half of fantail nonskid gone.The captain would then want everything shipshape to go into port the next morning.He didn't want anyone to know we fired a missle.So we worked our butts off rest of the day and into the night.
Anyway a sam can make a hell of a mess.