<span class="bbc_size" style="font-size: 12pt;">As the water continued to rise, it began to reach some of the transformers that kept the Vault properly supplied with power.  Normally, these transformers would be safe from most moisture, but given the amount of water being dealt with, it isn't long before the transformers have water inside of them.  This causes them to short out, blowing the transformer and electrifying the water, killing anyone unfortunate enough to be in the water at the time, as well as overloading the lights and making it pitch black inside the living quarters.  The only way to stop the power flowing to the flooded compartments would be to shut down power to that part of the vault, which will be tricky given that the local cutoff is now in electrified water, and the only other option would be to shut down power to half the vault.</span>