Constructive waves are low energy waves that deposit materials on a coast.
As the waves approach such as coast, the friction between the waves and the sea bed causes the waves to slow down at some distance from the coast.
The waves break gently over a long distance.
Swash is powerful than backwash, the more materials are carried up and deposited on the coast than are removed.
Over time, the coast is built up.
Destructive waves are high energy waves that’s erode a coast .
They are common along steep sloping coasts where they are break with a great force over a short distance.
The backwash of the waves is more powerful than the swash.
More materials are removed than are deposited on the coast.
Over time , the coast is eroded away.