Revealing mistake: The Acheron fires many devastating blows on the Surprise and the effect is visible in close-ups and a wide shot. However, after Mr. Mowett yells, "Relieving-tackles on the tiller! You men collect the wounded!" there is another wide shot of the Acheron in the foreground and Surprise in the distance. In this shot Surprise has NO damage whatsoever! (00:11:00)
Revealing mistake: After a close-up of the drawing of one-armed Lord Nelson, Killick opens the lid of the steaming food for Jack in a close-up, just before Killick says, "Oh, here we go again. Scrape, scrape, screech, screech." Later, after Pullings takes command of Acheron, Jack tunes up his violin and Killick says, "Here we go again," in another close-up of the steaming food for Jack. Every detail of the food shown in both close-ups is exactly the same - obviously shot at the same time. (00:26:25 - 02:05:20)
Continuity mistake: When Stephen removes the bullet, the rope's knot on the pillow, to the right of Stephen's head, appears, disappears and reappears. (01:31:55)
Continuity mistake: While Jack and the rest speak about Lord Nelson, the plate of bread on the table is visible when the wide shots face Stephen. The following two close-ups show the plate of bread on the table, as Stephen looks at the weevils and the bread is positioned very differently in these shots. As Jack slams his hand down on the table, the bread is positioned as in the previous wide shots. (00:32:45 - 00:34:25)
Continuity mistake: While Stephen performs Blakeney's amputation, the string on the hinge of Stephen's eyeglasses changes in consecutive shots. (00:21:45)
Continuity mistake: As Stephen holds the diary, in the shot facing him he begins to flip the page with his right hand, yet, in the next close-up of the diary he flips the page with his left hand. The actual pages he flips and the way he holds the diary differs in this and following shots as well. (01:34:25)
Continuity mistake: As Higgins studies the medical diagrams while sitting next to Stephen, when he turns the page he gasps and covers his mouth. The diagrams on the page in the close-up differ from the ones in the wide shot as Higgins still has his hand over is mouth. (01:27:50)
Continuity mistake: In the tent before and during the removal of Stephen's bullet, the ropes at the top of the tent behind Jack differ in the close-ups and wide shots. (01:30:40)
Continuity mistake: As Higgins removes the piece of cloth from the bullet and compares it to the shirt, the blood on his hands and the way he holds the shirt differs in the close-up and wide shots. (01:32:50)
Chosen answer: The flag is a signal flag, and is probably meant to signal that the ship is a whaler or engaged in fishing operations. Such flags were part of an international code, which, with some modification, is still in use today. (The flag is similar to the modern-day "Foxtrot".)