Imagine that you were one of the boys trapped on the beach what you did from the time you were cut off by the tide until you finally reached the top of the cliff . describe in 200 words ?

You may choose to write about a number of things. Firstly, you can say how, at first, you enjoyed the freedom, and the nice weather, and the sea. As time went by you can start to show how your initial enthusiasm disappeared, and how you had to adapt while waiting for help (i.e. try and find shelter, some food, learn how to hunt, catch fish etc). Eventually you come at the top and see...? You may chose to have a depressive ending, or an optimistic (e.g. you see a ship approaching).
Hope that gives you some ideas!