That is a fascinating operation. I can understand why they want all vehicles destroyed. One time I was working on a boat in the Chesapeake Bay and dropped a Craftsman chrome ratchet. It was only about 3 feet of water so I wasn't worried about immediately retreiving the ratchet. It was in the water no more than 10 minutes. When I found it, it was already showing a few spots of corrosion where some seaweed had touched it.
Boat motors have something called a sacrificial anode which corrodes to help prevent corrosion of the motor itself. I can only imagine what 8 months of submersion in shallow, oxygenated, warm salt water would do to cars.