When Captain Ambrose arrives in France, a close-up shot shows him taking the cotton wool out of his ears. In the next shot, the cotton wool is still in his ears.
When the R.M.S. Arabella splits from the rest of the pier and drops into the sea, it is obviously a model with model figures of Captain Ambrose and Tommy (No. 1). In the next shot they are both in entirely different positions on the now floating ship.
At the end of the movie as Captain Ambrose is being carried up the beach after sailing to shore, he removes the cotton wool from his ears so he can hear the crowd cheering in French. The next shot sees the wool back in his ears, though it is also clearly a dummy being carried shoulder high.
The rat seen abandoning the R.M.S. Arabella is obviously an animated model.