Engineer Ramsey of the Merrimack makes a number of comments about having problems getting power due to the smokestack being damaged, yet in subsequent pictures the Merrimack's stack shows no damage.
When the Monitor first appears from behind the Minnesota there is nobody on deck. But in the next close-up the Monitor's captain and her officers are standing on deck.
After pulling free of the mud bank, Jones informs Simms that he is turning to give him a port-beam broadside. The Merrimack then proceeds to fire its starboard guns exclusively throughout the exchange of fire that follows.
The U.S. sloop Cumberland is shown being destroyed by gunfire. In the actual battle it was sunk by ramming.
During the first battle between the Merrimac and the Union ships, some cannons tumble, bounce and womble when recoiling or falling on top of the sailors, revealing they are actually lightweight props.