The Great Barrier Reef is home to six of the world's seven sea turtle species. Turtle hatchlings weigh only 15-30 grams at birth and measure 5-7 centimetres on average. A fully grown leatherback turtle can reach a length of 2 metres and weigh up to 900 kg. At the other end of the scale, olive ridley turtles grow to a length of 1 metres, but weigh in at a humble 45 kilos. The estimated lifespan of sea turtles range from 60-80 years. Rock on, dude!