Looks verry nice.
And since you are using layering why not try and make water tiles semitransparent and then render the botom textures below, closer to shore more visible the botom texture is. This way you could get the impresion of increasing water depth which would look realy nice.
Also since you are using layering you might wanna go and use larger textures whose dimensions are actually bigger than tile dimensions. This way the textures will look less repetive (you can clearly see repetive paterns in water texture in the left picture).