I think once you are on the surface, your chances rapidly grow, even when its cold water with a lot of current. You still only have to manage to get 20-30m to the side out of the strongest current. The way to the surface in time to not suffocate might be the problem, especially out of a wildly tumbling car that smashes against rocks and stuff in the riverbed while being hurled on by a powerful current.
I think once you are on the surface, your chances rapidly grow, even when its cold water with a lot of current. You still only have to manage to get 20-30m to the side out of the strongest current. The way to the surface in time to not suffocate might be the problem, especially out of a wildly tumbling car that smashes against rocks and stuff in the riverbed while being hurled on by a powerful current.