If someone's boat got tossed into the air and smashed into the ground because of a micro-burst, it is an "act of god" and subject to that clause (if it exsits as an exclusion) in the insurance policy...i.e. the insurance company may not cover the damages unless your policy covers "acts of god". HOWEVER, I'm pretty sure that if the same owner was negligent in some way (like not securing his boat from flying into the air in such a scenario) any damage done to other boats is no longer an act of god but is a liability issue - and even home owner's and renter's policies should cover this. They won't cover the boat that flew through the air but they should cover the damage inflicted upon others.