Well, that was my first thought after seeing this on Dr.Phil and having no knowledge of the case prior. I just thought instantly of him maybe reaching into the lake to grab a fish or something and falling. I didn't get a vibe from the Dad that he was lying, I thought he seemed ashamed that Dylan disapeared while under his care and he was taking a verbal beating from the Mother. Anyway, I don't know what the motive would be. You don't just all of a sudden "snap" and kill your 13 year old. I mean, I'm sure it has happened, but the father didn't seem like he was suffering from some serious mental breakdown and if he was... would he really have the capability to cover it up this well? Transport and hide his son's body and throw it away? Think about it, parents who kill their own child in a "moment of anger" usually make up some kind of accident story. They can't throw their child's body away, they do what is easiest. There is always a motive, always, and I just don't see what it'd be.