Other mistake: When the students are below deck having a meal, a glass pitcher of orange juice can be seen. Even though the boat is apparently rocking to and fro in the waves, the juice level stays still. Obviously it is the camera that is moving and not the set.
Other mistake: When the Cuban ship approaches, the guy on the Albatras ship starts speaking Spanish using a megaphone. They cut to the Cuban guy, and then cut back to the guy on the Albatras speaking Spanish, and although you hear his voice sounding like its coming through the megaphone, there is NO megaphone to be seen.