A 15-year-old girl visiting Tybee Island, Ga., with her family from Alabama was killed Saturday by a lightning strike. The teen was swimming off the coast at the time, CNN reports. As NOAA explains, lightning usually strikes land, but when it hits the ocean, the water acts as a conductor. "Often swimmers and beach goers are enjoying the moment and when storms appear suddenly, the unthinkable can occur," the island's mayor says. Lifeguards and firefighters attempted CPR, but the girl was declared dead at a hospital, WJCL reports. (More Georgia stories.)