'mmm
modern electrical installations have RCDs which would cut the supply in the event of water getting onto connections, and I have great doubts about being able to start a fire that way. When substations get wet, after draining, they often turn the power on momentarily to boil it off the switches (best not tell your son that). But water leakage is a common cause of breakers tripping, and in an older installation can cause shocks, especially if you touch earthed metal such as a tap, pipe or electrical appliance at the same time.