I've read many unflattering comments regarding this film, and the only things I have seen that they all have in common are: "boring" and "unrealistic".
First of all, they used real frickin' crocs! How much more realistic can you get? No CGI, no animatronics, no miniatures. Just a croc and a piece of meat. Have fun, fellas!
There is no question that this film gets off to a slow start. Character development, what little they had, anyway, does take a bit of time, and I think this is primarily where this film lacks.
However, when the film gets going, I found the action picked up dramatically. I don't mean to say that there is a lot of action. If anything, there are more moments where the croc can't be seen at all, and the people are just waiting. However, we know that there isn't going to be any relief, and that the croc is just biding its time. This had a similar eerie feel to other films that achieve their horror through non-action, such as Open Water (another film that has been criticized by some viewers as being "boring"). Personally, I think that viewers who find themselves incapable of feeling the suspense have had their attention spans surgically removed at birth, but that's just me.
Finally, the characters feel real, and the situation is such that it really could happen to anyone in the right circumstances. Furthermore, the deaths are completely real, and at times, it's a little tough to watch.
All in all, this one's a winner.