How can I turn off electric water heater if...?

So basically the Thermostat doesn't work and we have been hitting a on on it that turned it on and when the heater got too hot it would flip off... well today we have no hot water and the heater is making a whiney sound... we think it is because the heater isn't heating up anymore so the switch won't flip off but now it is contiually going and we can not turn it off... the obvious solution is to pull the breaker but the last person to live here wired it with half the house so we don't know what to do apart from living in a dark, powerless house with it off... any solutions to what the problem might be and how to fix would be great..