Revealing mistake: The ship is being attacked by a megalodon. The USS King is supposed to be in open ocean. When three sailors run to the left, we can see the ship is next to a dock. (01:01:35)
Factual error: The USS King's crew are all wearing blue camos with US NAVY on their left chest. Yet the Skipper keeps calling them Marines.
Other mistake: On the USS Fragasso, everyone is in uniform, except the Skipper. He is wearing a blue polo shirt with no markings or rank.
Character mistake: The Captain of the USS Fragasso comes onto the bridge. A Petty Officer says, "Officer on deck," and salutes while looking out the forward windscreen. He should have said, "Captain on the bridge" and not saluted.
Factual error: Lieutenant Commander Sharp addresses the crew of the USS King. At the end, he shouts "Semper Fi." Marines say "Semper Fi," not Navy personnel. "Hooyah!" would have been more appropriate. By the way, I don't think bright metal collar insignias are worn with the blue camo uniform. They use subdued rank insignia. But I am not sure.
