RedactedNarrative: The watercraft was towing a tube behind it with 2 passengers on the tube and 2 persons onboard the boat. At one point, when the operator began to accelerate, the motor began shaking and moving around loosely as if the motor was not firmly attached to the watercraft. The watercraft suddenly began to fill with water, coming inside near the rear of the boat. The watercraft filled with water and slowly sank in the shallow water and the occupants jumped out of the boat. The watercraft was towed back to the public access by another watercraft that was on the lake. It is believed that the boat was so rotted and in such poor condition that the motor punctured through the stern of the hull and water then flowed through the openings around the motor and into the boat. No injuries occurred in this incident. Life jackets were being worn and alcohol was not a factor.