40 meters of water is equal to 56 PSI pressure. We are used to 14PSI atmospheric pressure. PSI is pound per inch ,one pound is about 0.5kg. To dive 40m one must carry 56 pounds per square inch of his body. To understand this, if you dive with an empty bottle of water ,the bottle will collapse .
A human body pumps blood at 2PSI ( systole). Increased pressure increases your body rate of absorption of gases within your body, a phenomenon called narcosis ,have same effect as narcotics in a human body Narcosis produces a state similar to drunkenness, alcohol intoxication. Imagine diving sober only to feel drunk at 40 meters deep .
That place is truly alien , weird animals ,sharks ,reduced light level, temperature at 4°c, its possible to lose life while looking for lifeless bodies. The ocean also got some serious currents ,might prevent one from resurfacing
Water is 800 times denser than air, so it creates resistance magnitudes stronger than the resistance caused by even a storm-level wind.
Since we have accepted what happened, if the rescue effort proves to be difficult and risky like in the titanic and numerous ships lying under sea, the family can use the sea bed as a place for burial .I hope the car windows were closed, if not so, then there is no need of retrieving the bodies, they might not be there .