Watch Free Online HD Moviesjoy. An old, battle-scarred hippo bull – once a king among the hippos in Zambia’s Luangwa Valley – has an incredible story to tell. It’s a story normally hidden from human eyes and almost always misunderstood, because a hippo’s secret life happens beneath the water and under cover of darkness. Follow the life of the “Hippo King,” and discover the true character of one of Earth’s largest land mammals.