Factual error: The shark follows Brody into the sunken ship (yeah, right) and eventually the chase ends with the shark at the end of a very narrow passageway, with no room for it swim further forward, and no room to turn. Since the rigid nature of a shark's pectoral fins means that they cannot swim backwards this one would be stuck. And since Great White sharks have to constantly swim in order to breathe, the movie really should have ended right there.
Factual error: The shark that attacks the Brodys in the Bahamas is presumably the same one that kills poor Sean Brody on Amity Island (that poor kid can't catch a break). Ellen departs for the Bahamas after Sean's funeral and the shark follows shortly thereafter. So, the shark swims from Amity, an island off the North Atlantic Coast, down to the Bahamas in order to stalk Ellen, Mike, etc. in a matter of days. Hmmm. As Matt Hooper said in the first film, "fast fish".
Trivia: There are two different endings to this movie. In the first one (released on video and DVD in the US), the shark (inexplicably) explodes after being rammed by the boat and sinks to the bottom in a reuse of footage from "Jaws." When the camera cuts back to the survivors floating in the water, we see that Mario Van Peebles, though badly wounded, is alive after all. In the second ending (which can be seen on American Movie Classics in the US), Mario Van Peebles does not survive his fall off of the boat; when he falls, he lands in the shark's mouth and is killed. Also, when the boat rams into the shark, it does not explode but is more "realistically" impaled, blood pouring from its mouth as it dies. After the survivors are knocked off the boat, there is a shot of ship and shark sinking to the bottom, prow of the ship stuck in the side of the shark.