Untitled Sighting

While at our cabin at Castor River in Bollinger Co Missouri our 14 yr old son and his friend witnessed what they said appeared to be a 7-8 ft tall human like creature knock down a dead tree across the river in their direction. (my wife and I were at the spot the day before and the tree wasn't there..when we went the next morning we seen it in the river) It then landed in the water and stood there, it started towards them and they ran back to our cabin. Before this happened they heard rocks or something being thrown into the water. This occurred about 10-11 at night while the boys were in the river gigging. Which is knee to waist deep. These boys are all boy and spend nights out in tents at the river and woods.. This night they were extremely upset and scared and wouldn't stay in the tent. They wanted to leave that night and come home! I don't know what they seen, but I don't think they are making this up, they were truly scared!!