The film used very little CGI. The crocodile was real and practical effects were used.
Based on a true story. Two teens became trapped in a mangrove tree in a river after an adventure trip in the Northern Territory of Australia. After a third member of the group slipped into the river, the two others jumped in to try and help him. As it turns out, a saltwater crocodile was nearby, who then attacked and killed their friend. The crocodile circled and stalked the two others overnight as they clung to the branches of the mangrove tree. Though they were rescued the next day, their friend was never recovered.
The crocodile appears to remain unseen throughout. In reality, crocodiles and other crocodilians typically don't stay under longer much more than 15 minutes, and over an hour in extreme cases.
One of two Australian crocodile movies made and released in 2007. The other picture was Rogue (2007).
The little doll on the boat is Cebolinha, a Brazilian famous comic-book character.