The dugong is an Australian cousin of the American manatee. They are herbivores that can grow up to 10 feet in length and weigh between 510 to 1,100 pounds. They are found in the shallow waters along Australia's north coast, including the Great Barrier Reef. Due to their size only large veracious predators can successfully prey on them.
The tiger shark is a predator which can reach lengths of 14 feet and weigh between 850 and 1,400 pounds. They are found in tropical waters around equatorial regions and can be found of the coasts of the U.S., South America, Africa, India and northern Australia. Tiger sharks are known to eat just about anything they can scavenge or kill and have been found with tires and license plates in their stomachs. They can be solitary or part of a shoal and will attack anything they feel they can manage, including dugongs.
The bull shark is smaller than the tiger at around 11.5 feet in length and weighs between 200 and 500 pounds. They are found in tropical or subtropical waters close to the coasts of the Americas, Africa, South Asia and northern Australia. The sharks have also been recorded far inland in fresh water rivers and have been linked to many historic attacks on humans. They have a reputation as fierce hunters and will attack and eat almost anything, including dugongs, dolphins and other sharks.
The orca, or killer whale, is a huge predator reaching lengths of 32 feet and weighing up to 6 tons. They can be found in coastal regions worldwide in tropical or arctic waters and commonly off the north coast of Australia. The name is misleading as orcas are not whales but are in fact the largest member of the dolphin family. They hunt in family groups known as pods that can number 40 individuals, feeding on fish and other marine mammals such as whales, dolphins, seals and dugongs.
The saltwater crocodile is the planet's largest living crocodilian. It can reach lengths of up to 23 feet and weigh between 1,000 and 2,200 pounds. They can be found in fresh and saltwater habitats in southern Asia and northern Australia. Large specimens are capable of catching and killing large land and sea mammals using stealth and ambush techniques. The crocodile catches its prey and drags it below water to drown. Sharing the same habitat, the dugong is on the list of animals a saltwater crocodile will hunt.