Continuity mistake: When Blakeney and Padeen run into Stephen's tent, Blakeney says, "So I've made a few notes, if you want to see them," and he hands Stephen the diary. The way Blakeney holds the diary, as he hands it to Stephen, differs in the shot facing him and the next one facing Stephen, note the clasp on the diary. (01:34:15)
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: After fighting aboard Acheron, when Jack sorts through some rubble with his sword and as he is stabbed, the items on the ground differ in consecutive shots. (01:57:10)
Continuity mistake: The blood stains on the front of Jack's shirt change drastically in the close-up, when he is stabbed, as compared to the previous and following shots. (01:57:15)
Continuity mistake: The position of the needle and thread lying on Peter's body differ in the wide shot and following close-up. (01:59:10)
Continuity mistake: In the close-up of the deceased, Mr. Allen lies right beside Peter and Blakeney's knees are visible above Peter's head, while he mourns over Peter. However, in the wide shot as Blakeney still stares at Peter, Peter and Mr. Allen are now much farther apart as Davies sits between the two. Peter and the hammock's position differ in his next close-up as well. (01:59:30)
Continuity mistake: In the last shot we see the Surprise make a sharp 90 degrees turn to follow l'Acheron to Valparaiso. It seems that the wind changes 90 degrees in the same instant, because it is not necessary to trim the sails, and the pennant keeps flying in the same direction relative to the ship. (02:08:05)
Continuity mistake: There are two tight close-ups of the words "hold fast," which are tattooed on Joe Plaice's fingers; When "Engaged enemy frigate at six bells," is said as Joe speaks, and as Stephen performs the brain surgery on Joe. The letters noticeably differ in the two shots, particularly the l, d, f, and t.
Continuity mistake: The blood on Jack's shirt constantly changes during the final battle with the Acheron.
Continuity mistake: The order is given to closereef the topsail. But moments earlier, you see seaman doing just that, working on the last reef.
Chosen answer: They stop singing because they hear Hollom joining in. There are very strict ranks in the Navy, and Hollom singing with the lower crew dissipates these ranks, which is undesirable. That Hollom sings with the crew is frowned upon by the captain, as can be seen by his serious/agitated reaction after Stephen mentions that Hollom has such a clear voice.