South-east Asia
The fish more terrifying than a piranha has been uncovered in Britain causing widespread panic. The snakehead eats just about everything it comes across, and has been known to kill humans. To add to the horror, it can survive on land for four days and grow up to the 3ft long.
In 2002 a snakehead invasion across America saw snipers camped by the water with "shoot to kill" orders and even entire lakes being poisoned to stop the species from breeding. As they're illegal in the UK and no one knows where this 2ft beast came from, there's understandable anxiety.