Black Water (2007)

What begins as a family vacation to the mangroves of Northern Australia ends up with a crocodile attack and a fight to survive in Black Water.
Reportedly based on real-life events, the movie is inspired by a crocodile attack that had happened in Northern Australia in 2003.
The film used footage of real crocodiles (as well as some CGI) to create the vicious monsters that are portrayed in the embellished story.