Hello Rassman.
I did see on another thread something about the swiftboats firing in case of enemy fire. And someone pointed out that, being in water as he was, Rassman likely wouln't have been in a position to tell the difference.
Believe me, when we were fired upon all hell broke loose. I recall one incident on one of the boats in our division where the gunners mate on the twin .50s froze up on the triggers and one of the barrels warped resulting in a round exiting through the side of the barrel and through the pilot house.
I always figured the VC used to fire on our Swift Boats just to watch all resulting chaos.