Should you swim in an indoor pool when it is lightning?

Although it might seem that the pool is "ground" when lightning strikes, the electrical current from the strike itself is not limited to exactly the spot where the bolt strikes. Because there is resistance in the water and in the ground, there is a large voltage difference between the spot where the bolt strikes and to areas tens of feet away. If your body is within this zone, a voltage differential is built up across your body and a large electrical current can pass through you causing pain, burns, or death.