Moving upstream in Sabine River which was very low and clogged with obstacles, mostly downed trees.  Three people aboard - operator and two passengers. One passenger moved to front of boat and sat on deck near bow, facing back of boat. Other Passenger sat on back edge of front deck. Passenger near bow wore inflatable lifejacket. Passenger farther back on deck was not wearing a PFD.  Because of obstructions above and below water surface, I was operating the boat at a very slow speed - barely more than idle speed, probably about like a fast walk.  The outboard motor struck a submerged tree trunk, immediately stopping the vessel. Both passengers were thrown forward.  Passenger closest to bow tumbled out of boat and into river.  Passenger siting on edge of front deck thrown forward, striking right side on trolling motor.  Overboard passenger was quickly retrieved. (NOTE: "automatic" PFD failed to inflate). Overboard passenger lost a pair of prescription glasses costing an estimated $500.00.  Second Passenger suffered severely bruised and seperated ribs which required medical attention over the following week, including vistis to emergency care clinic, multiple x-rays, office vists to orthopedist, more x-rays, prescription medication, radiologist, etc.  Total medical cost: approximately $2000.00. No Damage to the Vessel.

Operator Completed Report.

Paxton                        