When Cliff is saving his daughter, he uses a board to help her across. When first shown, it looks brand new, and when they are going across it, it's clearly a different, more rotten looking one. It changes from scene to scene.
As the little girl crawls over the plank an aerial shot shows no plank.
Although the ship is supposed to be either British or American, most of the playing cards in the engine room are in French, plus in several scenes pressure gauges may be observed. It appears that most are reading zero, indicating that only two boilers were lit, and at reduced pressure - probably to supply service steam to alternators for the ship's power.
In the final shots of the ship sinking, the nearby coastline can be seen reflected in its outside windows.
When the first explosion goes off in the dining room, you can see the piano player as clear as day, with out any arms or legs, so hence this is a dummy.
In several sequences on the bridge, some of the windows are alternately closed and open in different shots within the same scene.
In the final scenes of the ship sinking, as the characters jump into the water, there is an inrush of sea water onto the deck. The ship's bulkhead clearly bends over with the weight of this water as this is obviously a wooden film set and not the real ship they jump from.
In the scenes where there are explosions in the public rooms, it's quite obvious that the "victims" are actually dummies.
In the final scene of the ship sinking as the characters leave it, a crew member in full scuba gear can be seen.
As the Captain and his two officers leave the dining room to check on the fire, the shadows of the boom microphones can be seen against a wall behind them.
When the Captain finally gives the order to send out an SOS, the radio operator says the wrong name of the ship twice.