On land, the Nile hippopotamus appears massive and ungainly — and that's not surprising, considering these beasts can weigh up to 6,000 pounds, have eyes that seem to swivel on stalks and boast gaping mouths that expose curved canine teeth. But under the water, these behemoths become one of nature's most graceful creatures. Found in the Anheuser-Busch Hippo Harbor in the River's Edge zone, the Saint Louis Zoo's hippos can be found tracing balletic circles on the bottom of a 55,000-gallon aquarium. Behind a glass partition, they push across the floor with stubby legs and let loose jets of water from their nostrils as they break the surface. If you watch closely, you might be lucky enough to see the hippo's propeller-like tail spraying its poop underwater — thus feeding and nurturing an entire ecosystem. Ah, nature, you're so wonderfully gross.