The idea of the ocean receding into land is a great one, and I think if the ocean receded, it would be better if the individual species left behind had Marine characteristics, and now when it recedes, it's clearly land, which feels a little bit out of line. If you go from amphibious, to shallow water, to deep sea, the race moves along, it feels more comfortable. It doesn't seem realistic at the moment, but it would be great if it could be implemented in the form of dlc in the future.