That's right. Wake has electric wounds where the wires are, and only there. So at best, she jolted the water. But there's already a radio in the water. If she was going to all the effort of putting a radio in there to make us think anyone could have done it, she might as well actually let the electronic radio be the coup de gras. The only reason to use the jolt would be if she had to finish him off faster. Wake was almost definitely unconscious and not struggling, not to mention the culprit probably wanted us to think Wake died at the moment Ursula tripped the wire. So the culprit had all the time in the world.