Here in NE Louisiana we have had the wettest Fall that has ever been recorded, with a lot of flash flooding in our area since Labor Day. On the horrible, rainy, flood days, I would drive the 300sdl. The air intake is very high up on the front of the radiator and my belly pans are intact, except for the rear one which is missing in action. ( Can't seem to find a used one anywhere ) My 2007 BMW 530i on the other hand has it's air intake for the motor down low in front. I would be very afraid to drive in deep water with it.
In fact are you ready for this? A friend has a 2009 BMW M3 and he came upon a flash flooded area in his subdivision 3 weeks ago and drowned his M3. It was at night in a driving rain storm. He hit the water at about 30mph and it was about 18 inches deep. The car immediately went dead. The BMW dealer is draining alll fluids etc... but I believe the insurance company will total it due to internal water damage to the motor.

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John
1986 300sdl
1985 380se