??? a few feet of flood water? We are not talking 30 feet of water here. Perhaps it had been covered with a log or heavy underbrush. Only LE knows. Tim did see the depression...indicating that the weight of the bag had created such a landform over time....perhaps indicating it had never been moved at all.
So, yes, I supose if you want to go with that fact....that someone planted the bag or added to the bag or took things out of it... sure that thinking might be okay for you.
I respectfully just do not buy at all that this crime was some elaborate work of many....just the simple (and simple minded) work of one Casey Anthony. I would suppose with her Nanny labyrinth she had expected the bag to be found sooner and LE buying her babysitter story and looking for the babysitter. She didn't plan on (cough) the real work that LE does do and the fact that they would ever consider HER to be the murderer.
In an interview with MN yesterday (orlando sentinel here is link
http://www.orlandosentinel.com/news/local/orange/orl-caylee1408dec14,0,7966803.story ) he says that now remains have been found he can speak his thoughts and that from being at the center of this for a long time he has a really strong feeling of what occurred and that it was Casey. He wants to do nothing to help her Casey whatsoever. In short she did it (paraphrased but you can see it in whole at the link).
The only elaborate part of this crime, in my opinion, was the lies. The murder, where she put the body, and how she acted afterward were nothing but elements of the simple sociopath that she is. Finding the body close to her home, according to many experts, was to be expected with infanticide.