I have a 19-foot power boat & was creeping up on some wrecked river barges to take some pics. I was probably 75' away from the nearest visible wreckage when my outdrive struck something. It was like we hit a brick wall. I trimmed full-up & backed out. Later inspection revealed a notch in the leading edge of my outdrive unit. No real damage but I learned something that day. Get close but be very careful.