What is the difference between constructive and destructive waves?

So, constructive waves are the waves that build up the beaches. They have a large 'swash', which means they can carry deposits of sand and other materials far up the beach. They are much lower than destructive waves and have a longer 'wave length': this is the distance between the peak of each wave, or the top. Constructive waves are made when the sea is calm.

On the other hand, destructive waves are much larger and more powerful, and are mostly made during a storm. They have travelled a long way, and this is what makes them so powerful. Because they have a stronger backwash than swash, they erode the coastline because they take the sand back with them into the sea. There is a shorter distance between their peaks than with constructive waves (wavelength), and they are also much taller.