I found this movie to be engaging and entertaining plus it leads to a thoughtful moral lesson to kids who may watch it and even some adults who might not question their purpose in life or the history behind it. This is an essential plot point throughout the story seen in multiple characters. The biggest moral quandary here is that no one remembers why they are where they are. The "Dark Times", as the movie calls it, was a time where monsters would rise from the sea and pluck people from the shores to consume them. A specific area is mentioned and later its revealed that the area that was the highlight for these ghost stories doesn't even exist. Jacob questions the book and then there is a line where Maisie says to Jacob "But the book says otherwise, and it's going to outlast both of us. So people will believe the beasts destroy towns that don't exist, and hunters like to say 'yar'". It's such a good way to pass the lesson that not everything you read is true and it's important to remain skeptical of information being received. The movie even takes a step forward with this theme, with Maisie saying "Even if you're a hero, you can still be wrong". There is a theme throughout the move of 'live a great life and die a great death' which goes lengths to show the characterization of the hunters. They live by this motto and when it's proven that they are the victims of war, rather than heroes; many characters' goals change. It's an interesting turn of events, showing that everyone in war is a victim. This theme hits home when Jacob and Maisie are underwater and they see the skeletons of ships, sea beasts, and humans all lying together on the sea floor. A large theme to manage and I think it was handled very well.
There's a lot more to say with the graphics, characters themselves, world building, and exposition delivery but I don't wish to bore anyone today so I'll leave it at that. A good movie I highly recommend for anyone to watch if they have the spare time.