Wooden Turtle Mum & Hatchling - GreenSea Turtles are one of the largest species of turtle. They can weigh 65 130 kg and measure up to 1. 2m long. Despite their huge size fully grown, they measure just 2 inches when they hatch! The largest populations are found along the coast of Costa Rica and Australia. They spend most of their time underwater and can go up to 5 hours before coming up for air. They are currently listed as an endangered species due to hunting, over harvesting of thier