Waves (swash) approach land at an angle. Waves (backwash) leave land at right angles. The prevailing wind determines the movement of the material in the sea and hence the direction of the long shore drift.
If this is explained correctly along with the usage of a diagram, 6 marks will surely be awarded.
REMEMBER - Only explain the concept of long shore drift, not how groynes slow down the movement of sand along the beach.
Formation of Caves, Arches and Stacks A - Waves erode weaknesses in the rock and erode a cave along the greatest line of weakness. B - Cave size increased by further erosion and opens headland at both sides. Other caves increase in size. C - A stack is separated from rest of land and continued erosion of the headland results in an enlarged cave and leads to the collapse of the overhanging rock 'roof'. The next cave is eroded and becomes an arch