We only have a limited sample of the effects of modern weapon systems, so I think they are worthy of consideration.
gCaptain has a report on the recent test launch of a Naval Strike Missile from LCS-4, USS Coronado, I would like to point out the video that shows the result of a hit by this type missile in an earlier test that is included in gCaptain’s report and posted above, and talk about not the damage that was done, but the damage that was not done.
The result, is shown on the video at time 0:55. The target of this earlier test was a decommissioned Norwegian Oslo class frigate. These are relatively small ships, 317 feet long and 2,100 tons full load, only a little larger than a Bear class cutter and considerably smaller than the average merchant ship.
The Naval Strike Missile has a 125 kG warhead, smaller than that of a Harpoon (just under 500 pounds), but still respectable. The explosion and the resulting smoke are impressive. The damage would almost certainly have caused a mission kill, wiping out critical command and control, sensor, and fire control systems.
On the other hand, it appears the hull is largely intact. In fact, the target did not sink, it was subsequently towed back into port. I have observed that sea-skimming anti-ship cruise missiles always seem to strike about 20 feet or more above the waterline. This may be necessary to ensure they do not strike waves as they make their final approach, but it also seems to limit hull damage. This kind of hit might not have damaged the propulsion or steering gear, particularly on a larger ship.
If the Coast Guard is required to stop a medium to large ship, bent on doing some mischief, I don’t think even a cruise missile like NSM, could assure immobilization of the threat.