The CGI in this film
Just to start off, I love good horror films. Jaws, The Shining, The Descent, 28 Days Later. I also am a fan of great visual effects, being in the Visual Effects industry myself as a VFX supervisor. I do have a few criticisms on the film's narrative and style, being that the ending felt a little too "stagey" compared to the rest of the film. Albiet it was still a great ending, just a change in tone from the rest of the movie. I loved this film, I thought it was unique and it was told in a way that reminded me of all those travelogue horror stories you read in the Reader's Digest or other magazines.
Onto the CGI in this film. It was minimal for sure, but it was used probably better than any creature film since I can remember. You get the presence of the creature. You feel the threat without having to ruin the film with an over-present menace. The crocodile acted like a real crocodile, it slipped around, it was fat and less mobile in the mid-section(something most croc and most monster movies ignore is the fact that ribcages don't really twist and bend) and it's legs moved liked real stubby little legs. Very impressed. Also the jaws looked very real and were accompanied by wonderful sound effects. Overall the texture and the wetness looked real and the creature was always lit properly. I also loved how it distorted the water. I'm sure they used some physical prop to integrate it.
It really seemed like the VFX team behind this film knew what they were doing. I give them huge props for making me believe in CGI. I work in CGI myself, but I know it's limits, and I know it has to be done right without excess to look real. There was no need for a puppet(even if there was one used I couldn't tell). But the creature effects in this film are my favorite since, and better than Jurassic Park.