It takes a brave and hardy soul to take a fishing boat (or a boat of any kind, for that matter) out onto the waters of Lake Michigan. One of America's five Great Lakes, the body of water has a major impact on the type of weather that citizens of Chicago experience; and it isn't a particularly positive one! Unless, of course, you mean the positive charge of the electricity that routinely shoots down into the water.
Lake Michigan isn't really a lake; it's a small sea, composed entirely of freshwater. Thunderstorms love freshwater; they can draw from them, ripping away electrical charge and powering up the clouds. In short, Lake Michigan is lightning fuel, and anybody who lives close to it is liable to get burned! The photo itself is the product of fortunate timing; five separate strikes wouldn't be visible to the naked eye, but in the split second the shutter went off it captured them all perfectly.