It's no revelation that this Peterson guy is smug and cocky to the point that it shocks and infuriates the public. His bizarre behavior, mannerisms and words in spite of these events bear this out. I suspect that this is due to an extremely deflating and disheartening reality: exhaustive searches are being conducted in places he knows will produce nothing. He was a cop for 30 years, he knew how to create a false trail and get rid of anything that could possibly be used as evidence against him. Where do killers often dispose of bodies? In water. After the initial "loose ground/shallow grave" searches, he knew they'd turn to water. So, he created an illusion that he put her in water. State police, FBI, Equusearch, Army Corps of Engineers, the body, the barrel, the other container...this guy is sitting there laughing--on national TV. He put Stacy somewhere knowing that she will not likely be found for a long, long time...probably long after we're all gone.
I'm sorry if I sound negative here, but a huge stroke of luck is what we need.