Update on waves hitting the beach

Having posted about waves on the beach at Blackpool, I had another look at St Bees. Once again it seemed to me that the wavelength increased as the waves came up the beach. I thought that the theory was that waves slow down in shallow water. This is why they bend as they come onto the beach. So I was thinking that maybe it is because the shallower bottom spreads out the material more - less depth so more width because water is incompressible. However, although I know that a water wave is a circular motion and not pure transverse, surely it is a movement of energy not material. It should travel over the water, not be a movement of water. I've tried to make observations and then work out explanations on this blog so will continue to watch waves to see if the initial observation really is correct.