RedactedNarrative: V1 was towing a tube with 2 grand kids in the tube.  The operator turned to check on the tube & then turned to her daughter in the boat. While she was looking at her daughter she ran over a navigation buoy and the chain tangled in the prop of the boat.  The buoy was cut in half by the prop and the chain and buoy damaged the prop, skag, & lower unit of the boat.  The boat was towed to a dock.