Completely absurd.
If someone is “drowned”, no doubt they are dead.
But the average person without training doesn’t know one way or the other for sure. SOMEBODY would have called SOMEONE asking for first-aid, whatever.
Sure we do! Who covers up an accident by making it look like a murder? No one.
The baby drowns in a pool, not an uncommon thing to happen in Florida, and instead of calling 911, someone wraps duct tape around her head, puts her in a couple of bags, drives around with the decomposing body for a few days and then tosses her in the woods.
Ridiculous theory, I don't care how weird the family is.