It happens rarely, and, yes, when I've seen it happen, it has almost always been someone young on a PWC or someone driving a rental boat. I've never seen a 38' Baja drive in there
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The only exception to the "young and/or inexperienced" is the guys who are bass fishing that come through slowly. We have had some good size smallmouth taken right off our dock. The fishermen go very slow of course, and they are looking around for swimmers and obstacles, so no problem as far as I'm concerned.