2.8 rating is a joke!
The only thing I can figure for this ridiculously low score is that, because the first movie is a cultural phenomenon, a lot of people who have never seen a b-movie in their life ended up seeing this. This isn't a great movie by any means, but it is far from bad. Sure, it's very unrealistic for a fish to hold a grudge, but that doesn't stop this from being a fun monster movie. I consider myself a b-movie connoisseur, and believe me, I have seen far worse movies with far higher scores.
"Aliens? Us? Is this one of your Earth jokes?"