Open-world and mobile

Hello everybody,

I'm planning to make an open-world 3D game for mobile, and I'm worrying about performances. It will be a racing game in some tropical cities, so there will be city-islands, water, bridges, cars etc. So I don't know how to proceed to make it work flawlessly. I was thinking of setting up a script that will hide the renders when they are far from the camera, but would it be enough ? And I'm worrying about the terrain and the water, because we can't "split" them.

Anyone have some experience on the subjects or advices to give me ?