Why is it a goof not to design the car to survive complete salt water immersion? Combined with protecting all the electronics and interior, I imagine that would

Why is it a goof not to design the car to survive complete salt water immersion? Combined with protecting all the electronics and interior, I imagine that would add a large price to every single car for a situation everyone knows totals the car anyway. I don't think I'd pay anything extra for that feature, at least.