Corrected entry: When the ship enters the Lair of the Sirens, Marina calls for Spike (the dog) to extend the the blades on the sides of the ship. But she's only been on board a day or so and has been locked in a store room. She cannot possibly know that the blades exist, let alone that the dog knows how to activate them. (00:32:20)
Corrected entry: When Sinbad and his crew reach the stone gates, Eris sends a frosty blizzard to sweep them with snow and ice. By the next scene, all of them are cozily swaddled in parkas and furs. My nitpick is two-fold; first, why would they have all this winter gear with them? They're a Mediterranean sailing vessel, and would almost never have to deal with arctic conditions. They shouldn't even have all these parkas. Second, Marina is wearing a perfectly-tailored, form-fitting jacket. If she was a stowaway, why on earth were they carrying a parka that was just her size?
Correction: I'll start with the second part. In one scene you can see all the sailors checking their gems that Marina gave them. Since she isn't a common stowaway (she bribed the crew instead of sneaking on), you can assume that she could have brought a little luggage with her. As for the winter gear Sinbad knew what direction he had to sail, and from this they may have known to bring some winter supplies just in case. It's a big assumption, but not entirely implausible.
Correction: The movie is not done in real time. There would be a huge gap in time there but it is not referred to a) - because it would be boring and b) - because this is a children's movie.