RedactedNarrative: Boat operator stated boat was near shore anchored when someone in the vessel noticed the rear of the boat was taking on water. The operator said he wired an auxiliary pump to help get rid of the water and flagged down a nearby boat to assist in getting them a tow. The boat was being towed toward North Pool ramp when it began to sink. Once water filled the rear compartment the batteries wouldn't function. Boat was towed near shore as they could get, ending near a tree that was protruding out of the water. All four of the sunken vessels occupants boarded the towing vessel and were transported to North Pool Boat Ramp where I made contact with them. Once the vessel was towed back into shore the following day, it was discovered that the bellows were dry rotted and mostly gone_