[doc1019]

Or both cars missed the same turn?

[BenLurkin]

That would be my guess.

[Boogieman]

That, or aliens.

[hoosierham]

I'll bet there are literally hundreds of cars and pickups submerged in lakes and rivers as a result of accidents ;that is in addition to many others sent there as part of a murder.There are tens of thousands of places where water deep ,and,or cloudy, enough to hide a car from casual sight, is close to a road.There have been at least three cases in the last couple years of people unfamiliar with the area driving down a boat ramp into a deep lake and drowning.The drivers had time enough to call 9-1-1 on a cell phone before going under.Note it is very hard to open a car door against the pressure of all that water and modern cars electic windows would be shorted out.It isn't easy to break out a window with the usual items found in the passenger compartment. How many must fallen asleep ,swerved to avoid a deer, hit an icy patch,etc. on the decades of auto use?
There have been two men killed in separate accidents on opposite sides of my small town in just the last few years and a neighbor drove into the creek a decade ago.Only one of the three was drunk.One was on his way to work.One was going to get a prescription filled.

[cynwoody]

Or both cars missed the same turn?

More than likely, given the 69-year-old and friends went missing a decade or two before the teens.

[Falcon4.0]

They had a similar situation in Delaware back in the 80's where the only reason they found out about people missing the turn is that the cars piled up so high underwater that the last cars antenna was sticking out of the water at low tide.
The first words from the diver that was sent to investigate was, "You need a parking lot attendant down there".