Hippos and crocs have lived side by side for millennia, but are they cozy bedfellows or arch-enemies? One is a hefty herbivore, the other is the most successful freshwater predator on the planet, so how do they manage to survive together in the same habitat? They each have a unique arsenal of attributes honed by centuries of evolution; muscle power, bite force and ferocious dentition give them the edge in their environment. But once a year, their peaceful semi-aquatic existence turns into a battle for survival.

• Documentary