The name of the movie "Natsuki Kugo" asked about is called "Black Water", which I just watched a month ago.
★Chinese title: Black Water
★English title: Black Water
★Year: 2007
★Country and region: United States
★Category: Thriller
★Director: David Nerlich
Andrew Traucki
★Starring: Maeve Dermody... Lee
Diana Glenn ... Grace
Ben Oxenbould ... Jim
Fiona Press ... Pat
Andy Rodoreda ... Adam
★Rating: US: R
★Length: 90 minutes
★Language: English
★Introduction
"Black Water" is adapted from a real case. The story takes place in Northern Australia, where newly pregnant Diana, her husband and her sexy sister take a cheap trip to a mangrove swamp. The murderous crocodile capsized the boat and ate the guide. They ran to nearby trees for shelter in panic. Then they were faced with the difficult task of crossing a river in an overturned boat, knowing full well that a giant crocodile lurked in the murky waters.