The damage caused by saltwater is devastating. Electrical connectors begin to corrode after just a few hours, but the SMELL is horrendous. I've seen lots of cars totalled because they sat in just a foot or so of saltwater. The insurance adjusters don't waste much time inspecting these cars. They know the car is junk.

With the 220 S-Class you don't even need a flood to cause flood damage!!! The water drain at the front cowl can get clogged by leaves and other stuff. When this happens, rain water pours into the front passengers footwell area and works it's way back to the rear SAM and fuse box. ML's have similar issues (but without all the electronics!). A car in this condition that sits in a downpour for just a few hours can be considered a flood victim.
Since it's fresh water though, the carpets can be removed and cleaned, the water-logged electronics replaced, and everything is fine. I've got several clients' who have gone through this and haven't had any water related issues since.

I've never had to inspect a car that's been underwater completely, but the amount of work needed to make it presentable would be far too great to be considered "patched together". It's hard for me to imagine a modern MB that's been thoroughly soaked, would function normally for a short time and then develop problems. I think you'd have some pretty serious issues right away. But hey, that's only my opinion.