I was running in the Atchafalaya near Cow Island in my 15' flat and as soon as I started going across one of those big eddies I hit a submerged tree, I mean a huge submerged tree, I ran up on it, full speed and when it hit the lower unit of my motor it jarred me to the front of the boat. all the while my motor had gotten kicked sideways, STILL RUNNING FULL THROTTLE mind you, fighting to get to the back of my boat while doing circles and taking on water in the middle of the Atchafalaya. When I finally got to the back of my boat and shut to motor off I just sat there and floated downstream and laying flat on the bottom of my boat with water still in it.