I placed stones up my river, but had some Challenges when the lag came and took over the game. The stones are not that big, but I think the mesh collider on all of them was a bit much for the scene. But I feel it was interesting that the stones was the thing to make the game be slow. But that made me take a decision. I will make the game complete with the gameplay before I focus any more on the design. There will always be more that I can change. For now it is more important to have a playable game to deliver then the perfect design.