In six seconds,a total of 3 waves crash onto the shore of the beach .
The distance between each wave crest on the water is 8 meters.
Wave length is the length between two wave crests that is the distance between two wave crests.
We know distance between each wave crest is 8 meters
Total of 3 wave crests, the distance between first and second wave crest is 8 meters
the distance between second and third wave crest is 8 meters
So wave length = 8+8 = 16 meters