There would be no electricity, since the automatic safety systems should detect such a failure and break the circuits, similar to what should happen if a cable fails in your bathroom. But assume not, to make it interesting. The way of shortest resistance is probably still through the cable. Or it would all go into the ground. I doubt that there would be any danger to a swimmer (that is not too close). Note that such cables are buried in the ground to protect them, or rocks are deposited on top of them.