The sea turtles developed from land turtles about 200 million years ago. Their legs transformed into broad fins and the armour gradually acquired a streamlined shape to generate less resistance while diving. Due to its flat armour, the animals cannot retract the head when it senses danger. Sea turtles spend their whole life in the sea and go on land only for laying eggs. The female turtles dig a hole in the sand with their flippers, lay the eggs in the whole (nest), re-fill the nest with sand and then return to the ocean. Hatching usually takes place at night, when there is a lesser chance of predators like seagulls being around. Once the young ones reach the surface, they instinctively head towards the sea.
