Velocity of a wave decreases as the water gets shallow. As described in- v*v=gh (v=velocity g=gravity h=depth) as v=fλ (λ=wave length f=frequency) Either f or λ has to decrease. But as f is a constant where the same emitter is concerned the wavelength decreases. Velocity is lower in the front of the wave than the back of it because sea gets shallow near the shore. So the wavelength decreases as it gets to the shore. But the amount of water is the same. So the amplitude has to rise. Water is pushed upwards. What are yor comments?