What happens when lightning strikes Lake Michigan?

Dear Tom,

What happens to lightning when it strikes Lake Michigan? Can living things in the water be harmed, and how far would one need to be from the strike to be safe?

— Bob Provost, Wheaton

Dear Bob,

Water is a good conductor of electricity, and “a good conductor keeps most of the current on the surface,” said Don MacGorman, a physicist at the National Severe Storms Laboratory in Norman, Okla. MacGorman adds that some electricity does penetrate the water right at the strike point. “So fish under a lightning strike can be killed. … But it has to be much closer than you do on the surface of the water.” A depth of 7 to 10 feet probably is sufficient to ensure safety. However, since the charge travels outward mainly at the surface, “Lightning strikes have killed or injured people at the surface more than 30 yards away,” said David Schultz, also of the NSSL.