OK, thanks for that but don't a lot of newer Mercedes cars have auto braking at low speed?
If the tarp was secured the car would have (should have) stopped on its own.

Assuming my assertion is correct about the start / stop function, I bet they couldn’t get the doors open. Power windows likely didn’t work in salt water either,

There's a small retention pond by my office. There have been two different vehicle deaths in it.

The first was superbowl morning several years ago. About 10 in the morning a guy was speeding in his pickup, lost control in a big radius curve next to the pond and went in. A bystander saw it happen and jumped in to save him. Too late, the driver drowned.

A couple weeks later the Houston dive team thought the pond would be a good place to practice. While practice diving, their guide rope caught on something. Turns out it was a submerged car. The car had been there for years. It was a little old lady who disappeared one morning on the way to work and was never heard from again. It was big news in Houston when she disappeared. Driving by the pond you wouldn't think it was deep enough for a car to even be submerged.

The point of this is apparently it's pretty easy to drown once the car is submerged.

Not sure why this is hard to believe at all. An older person failed to maintain control of her car. Sad but it happens daily.

BMW has the auto engine shutoff too. I like it. Saves fuel which can get expensive. Anything to keep going to the pump less is a good thing imo.

Next vehicle is probably going to be an i3.