There's an American movie that starts off with a python attacking a helicopter and then eating people, and the humans can't fight it.
Snake-Fish Monster or Anaconda is about the horror of a monster with the head of a piranha and the body of a boa constrictor. We have seen the killing power of piranhas as well as pythons in many movies before, and this time, the piranha and python have merged perfectly to become the latest water monster, which instantly increases its attack power by a factor of N.