The two different versions of this scene feature high polygon assets versus low polygon assets with shadows and normals baked onto them. The high polygon version of the scene features a detailed water and sand plane. The problem with high polygon assets in 3D graphics is that they are very computationally expensive and will result in sub-optimal performance in games.
Certain techniques such as baking, level of detail (LoD), and retopologizing can be used to optimize 3D assets for games. In this case, the normals from the high polygon water and sand planes were baked onto a flat single polygon plane as a displacement map. This technique results in 3D faces looking as if they are bumpy and detailed when in actuality, they are not.