Waves that aren't parallel to the coast

 

Almost always the waves approaching the coast are parallel. This is because as the waves move into shallower water, they slow down by refraction and thus they change direction. This orientates them so that they are parallel. It occurred to me that in deep water, this can't happen. In a swimming pool there is just an abrupt side so the waves don't refract; they reflect instead. Here at Silloth the tide was high against the prom so there wasn't much chance of refraction. The rollers were almost perpendicular. However, these were long wavelength and there are other much shorter wavelengths that need accounting for and explaining.