The dugong is a large marine mammal

Marine mammal

Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...

 which, together with the manatee

Manatee

Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows...

s, is one of four living species of the order Sirenia

Sirenia

Sirenia is an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. Four species are living, in two families and genera. These are the dugong and manatees...

. It is the only living representative of the once-diverse family Dugongidae

Dugongidae

Dugongidae is a family in the order of Sirenia.The family has one surviving species, the Dugong , one recently extinct species, the Steller's Sea Cow , and a number of extinct genera known from the fossil record....

; its closest modern relative, Steller's sea cow

Steller's Sea Cow

Steller's sea cow was a large herbivorous marine mammal. In historical times, it was the largest member of the order Sirenia, which includes its closest living relative, the dugong , and the manatees...

 (Hydrodamalis gigas), was hunted to extinction

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

, though the majority of dugongs live in the northern waters of Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 between Shark Bay

Shark Bay

Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...

 and Moreton Bay

Moreton Bay

Moreton Bay is a bay on the eastern coast of Australia 45 km from Brisbane, Queensland. It is one of Queensland's most important coastal resources...

.