Don't help boat thieves steal your boat! Always lock your boat and take the keys with you, according to the Insurance Information Institute. Boat theft is big business says Robert Bryant, Institute for Business and Home Safety. Thousands of boats are stolen every year and half of them are recovered. Marine police says that leaving keys in the boat is the biggest mistake boat owners make. So if you like your boat, and most boat owners do, lock it and take your keys with you.