Beneath the peaceful surface of Europe’s waterways lies a hidden danger. A colossal aquatic creature lurks in the murky depths. Over the past 50 years, it has colonized most of Europe’s rivers — even the most polluted. This intruder has become the largest freshwater predator in Europe … and it even hunts on land. So which fish species is capable of coming out of the water to catch birds? The answer may surprise you: the catfish. This cannibal fish regulates its own population. Only the largest and most voracious survive.