Firstly, the most important thing of surviving on a Island is to construct a shelter so that you are away the Suns heat. Put large sticks diagonally so that it is secure then, put sticks, leaves and vegetation so that you don't get to hot. If you find a cave you can keep that as your shelter. While you waiting for help to arrive find a good secure place to protect you and keep you safe from the blowing sand, splashing water and sea animals. A big sheltered spot will keep you away from the sun, however good eyesight and visibility is good to spot rescue plans and other vehicles.