Out in the open waters of the western Pacific Ocean, a saltwater crocodile (Crocodylus porosus) attacks a common bottlenose dolphin (Tursiops truncatus). True to their name, saltwater crocodiles do in fact cross the ocean around Southeast Asia and Oceania, and the remains of pelagic fish have been found in their stomachs, so it seems very conceivable to me that they could attack other animals in that part of the sea. Closer to coastal waters, saltwater crocodiles have been observed hunting marine creatures such as sharks, sea turtles, dugongs, and sawfish.