Knocking in Webster Parish, Louisiana

This occurred approximately 18-19 years ago when I was about 13 or 14--probably 1979. My mother and I were inside our home. The time was probably close to dusk, there was still a little bit of daylight left. The next thing that I remember was that my mother said" that it was awful quiet outside all of a sudden." Then we heard the dog, start howling and scratching to get into the house, which was remarkable in its' own rights because this dog was tied to a stake in the yard. This was a Big German Shepard that had to be tied up because if he ran loose, he had a nasty habit of killing any animal he crossed paths with. Anyway as soon as my mother opened the door to let the dog in, the dog literally knocked her over and went immediately into the bedroom under the bed. The door was still open, so I looked outside and (this happened very fast) I noticed how dead still and quiet everything was. I felt that little charge of fear race up my spine and I remember that the hairs were standing up on my arms and neck, and at that moment my mother came back ! and started to shut the door, when all of a sudden we both heard this SCREAM. It was not human, it was not any animal I had ever heard. It was almost like a cross between a woman's scream and a cougar. Since I knew that there weren't any cougars or women standing out on our dock, we both knew we were hearing something unimaginable. We then heard big sloshes of water, as if something great was passing through the lakefront. (Our House was only about 1/2 an acre up from the lake.) This whole episode probably only lasted about 5 minutes. We then noticed that the normal sounds of the swamp came back as if someone had turned the lights back on. We knew that whatever it was, continued down the lake. We heard from other families that lived along the lake that they had experienced the same thing.