The electric window thing depends on how it is all wired. If you have a simple 12-volt battery wired to an electric motor with a simple switch, and throw the whole thing in the water, it will work fine. Sure, water is conductive (actually, the ions dissolved in water makes it conductive, pure water is not) but it's not very conductive. Certainly not enough to immediately discharge the battery, or even to compete with the copper wiring as a current path. Eventually the battery would discharge itself, but not for a while. In the meantime, there would be plenty of available current to operate the motor if you closed the circuit.
Contrast that to some sort or fancier semiconductor-controlled circuit that takes low-voltage, low-current signals from window switches and then uses logic to decide to activate relays to run the motors. The actual current to the motor isn't actually travelling through the heavy-duty switch in the door that you are pressing with your finger, just a digital signal. That kind of system is going to get all sorts of confused and probably not work as soon as you toss it in the river.