I bought a pristine 88 300zx(non turbo) with 188k miles on it when I lived in Houston in 2002 and one morning I woke up to find my car FLOATING in the parking lot. Once the water subsided I found that the car was filled up to the top of the seat bottoms and (of course) the car was dead. I ripped all the interior out of the car until it looked like a empty can and had the car towed to my work which happened to be a Mercedes dealer. I then put the car on a lift and changed ALL of the fluids(tranny fluid was like grey pudding), spark plugs and battery and drove the car home that day.............and drove it for the next 2 years before selling it in still perfect running condition to my sister who totalled it out 3 months later(and never paid me a dime for it) with over 220k miles. I miss that car.
PS moral of the story is that you CAN bring a flood car back to life under the right circumstances................and NEVER "give" a car to a family member until it's paid for.