I would have to say crocodile. Powerful jaws, armored hide, the ability to travel on land as well as in both fresh and salt water. They also conserve a great deal of energy when swimming in open water by surfing the ocean currents. The have been constant reports of crocs that have been tagged in australia, showing up in paupa new guinea and some of the other island nations.
Amphibious Good, planking bad, can Roar, but lives in da sewer. sharks live in sunken ships, dey gots loads more friends and host feeds, but they only color grey in loads of blue, Neither got ears u can spot,
I wish I could have voted for both. For me, sharks just BARELY beat out crocodiles, but that's because sharks come in more shapes and sizes. And because of that footage from Planet Earth of the shark lunging from the water to grab a seal.
Crocs are tactically flexible. They're masters of their domain, and if you're talking about salt water crocks, then sharks don;t eclusively own the ocean. Crocks also have a leg up over sharks in that they can go on land and not be completely useless. In fact, even less so on land, they are very fast and have the vaunted Death Roll.