Champsosaurus was an aquatic reptile with strong jaws and pointed teeth for preying upon fish. In appearance and in habit this group of reptiles  closely resembled the modern, long snouted crocodiles known as gharials.  Like crocodiles and other marine reptiles like the marine iguana, this animal probably swam with lateral body movements, with it's limbs pinned tightly against it's body to increase it's streamline when it was hunting (fishing) for it's prey.