It's hard to escape the feeling that the shark was obsessed with Michael Caine, seemingly aware he was aboard a flight headed for the Bahamas and compelled to pursue him. Alternatively, maybe it sought revenge on Caine for his involvement in _Beyond The Poseidon Adventure_. The movie is technically sound, and the actors do a decent job, but ultimately, the narrative stretches believability past the breaking point. Was the shark possessing some kind of mental ability? Did Ellen Brody have similar abilities? And what about that piece of driftwood Sean Brody was holding on to while being attacked? It doesn’t really matter. It's possible the shark in the Bahamas wasn't the same one as before, or maybe the Brodys had a different shark for each day. Or it could all have been a dream – which would probably be the most sensible explanation. Still, I won't excuse the filmmakers here. _Guilty as charged. Case closed._

Source on TMDB