Interior cabin walls of the cruise ship show to be built of masonry, a material never used for general construction of a vessel.
When Rick McGraw is dressed like a woman, he drops the bag of money. Several of the bills are blank on the back.
When all the Navy SEALs regroup one of the SEALs says "all doors and hatches are sealed", you can see light coming through the top left of the door.
At the end when the Navy Seal is fumbling with the grenade, despite a large gas tank and large amounts of fuel everywhere, when it shows him on fire he is the only thing on fire and there isn't even any smoke anywhere.
When the two sailors find the chupacabra in the laundry room, the one carrying the over-under (two-shot capacity) shotgun fires three shots before ejecting the shells.
At the beginning of the movie, a group of men are seen making their way through a jungle on a Caribbean island. One of the creatures shown is a meerkat, an animal which is found in African deserts, not in Caribbean jungles.
Dr. Peña says "echoskeleton" instead of "exoskeleton" when talking about the external armor-like structure of the creature.