RedactedNarrative: On July 11th 2020 at approximately 1600 hours I responded to a call of a sinking vessel on Flathead lake in the Woods Bay area.  I arrived on location at approximately 1630 hours.  I first met with the rental company who had towed the boat to shore.  The vessel was a 20’ South Bay Pontoon boat.  The railing on the right side of the boat was bent to the outside at approximately a 35-degree angle.  The drivers console was broke away from its mounts and also bent over.  The front right seat was missing from vessel and the front left seat was detached from its mounts.  I estimate the damage to the vessel was several thousand dollars.  I reviewed the rental document, in which the renter had signed off all boxes on appropriate usage and safety.  
  I then talked to the renter and other people on the vessel. I determined that there were Eight adults and six children along with 3 medium sized dogs on the boat.  There were also two medium sized coolers.  One of the adults is a Quadriplegic in a heavy wheelchair.  The boat is rated for 11 persons or 1495 pounds.  The weight given by the adults, not including the kids, dogs, coolers or wheelchair is over the boats rating.  One of the occupants of the boat stated that too many people were forward in the boat.  When the boat slowed down, the weight of these individuals caused the front right of the boat to submerge causing water to flood the deck and the boat to list to the right.  Nearly everybody jumped or fell out of the boat except the wheel chair bound person, one other adult and a child.  The boat then rebounded to its normal position.  The renter stated that he was not going very fast at this point.  He also stated that everyone was wearing a life jacket.  There was very little wind on this day, and the waves were too small to be of any significant factor.
  My conclusion is that the act of slowing down, causing the momentum of the vessel to lower the bow of the boat, along with the excess weight on the front of the boat were the main contributing factors.