Because the dikes block the force of the incoming waves, the water instead digs away the sand at the bottom of the dikes, deepening the sea bed. The movement of the sand is not stable and many people who come to play in the water do not understand the danger.
玄機出在海堤，因為外海打進來的浪雖被堤防擋住，但堤外底部沙子反被海浪淘空，海床加深，海沙流動不穩定，許多弄潮人，不知海岸暗藏著危機與陷阱。