Dr. Peña (Esposito), a cryptozoologist, manages to capture El Chupacabra on a remote Caribbean island and smuggles it aboard the cruise ship Regent Queen, commanded by Captain Randolph (Rhys-Davies) with the assistance of his young daughter, and ship fitness instructor, Jenny (Simmons). The Regent Queen has been experiencing a rash of burglaries, and Federal Marshal Lance Thompson (Neal) is brought on board to investigate.
Unfortunately, crew members sneak into the cargo hold on their break; their curiosity getting the better of them, they accidentally unlock the contained holding the creature. It kills them and escapes into the ship. When bodies start turning up, all passengers are ordered back to their cabins. However, an old woman is trying to catch her Shih Tzu; she follows it into the casino, where she finds, to her horror, El Chupacabra devouring her dog. Seeing the woman a better meal, the beast attacks and eats her.
U.S. Navy Seals are called in to help stop the creature, but their efforts are hindered by Dr. Peña, who believes the creature's life is more valuable than the lives of those aboard. The Navy Seals are killed off one by one by the beast and Dr. Peña resorts to using Jenny as live bait to recapture El Chupacabra. However, he is foiled when the beast outsmarts and fatally wounds him. Jenny is saved by Lance and they meet up with her father, who has set the engines to explode as all the other passengers have been evacuated. They flee on a lifeboat moments before the ship blows up and sinks the ship, taking the beast with it. As the group watches the ship sink, Captain Randolph tells Jenny and Lance that he has decided to retire and write his memoirs.
John Rhys-Davies as Captain Randolph Dylan Neal as Lance Thompson Chelan Simmons as Jenny Randolph Giancarlo Esposito as Dr. Peña Paula Shaw as Millie Hartman David Millbern as Rick McGraw Luke Darnell as Ensign Peters Mark Viniello as El Chupacabra