Dugongs and Turtles

Females give birth underwater to a single calf every 3 to 7 years after a 13 to 15 month gestation period.
The calf will remain with its mother, drinking her milk for between 14 to 18 months, and following close by until 1 to 2 years of age.
They reach adult size between 9 and 17 years of age, and are known to live to 70 years.

The main dangers to dugongs are natural predators being sharks, killer whales, crocodiles, and external factors including injuries from motor powered boats, being drowned in fishing nets, and reductions in sea-grasses from environmental pollution.

Except when traditionally hunted by Aborigines and Torres Strait Islanders, dugongs are protected from being killed and hunted under legislations.
It is known that Aborigines in southern Queensland keep a record of injured, dead and living dugongs, and the conditions of dugong feeding grounds, somewhat similar to what government departments refer to as EIS's (Environmental Impact Studies)

Dugongs, also known as 'sea cows', are mammals which graze on sea-grasses. They grow to about 3m (10 feet) in length, weigh about 400 kg (880 pounds), and can move at about 22km/hr (14 mph).
They live in the shallow coastal waters of northern Australia from the Queensland/ NSW border in the east to Shark Bay in Western Australia. They also live in parts of the Indian and Pacific Oceans in warm shallow seas where seagrass is found.
They move through the sea by moving their spade-like tail up and down, and using their two flippers.