I guess I figured copper wire would also required amplification. Interesting on the return path. Where does the source connect i.e. one side of the "battery"

I guess I figured copper wire would also required amplification. Interesting on the return path. Where does the source connect i.e. one side of the "battery" goes to the amplifier (which returns to the sea, not the battery) and the other side of the battery goes to where? the sea?