RedactedNarrative: V1 was traveling down Lapile Creek toward the Ouachita River when it hit a submerged stump that caused the operator to lose control and the passenger to be ejected. V1 was a stick steer and the operator lost control of the stick when he was thrown into the bottom of V1. V1 made multiple circles before the operator could reach up and shut the throttle level off because he was not wearing his kill switch lanyard.  The passenger was able to re-enter V1 and drive it to the ramp to get help because the operator could not get up. 