Guy

The possible way, to make the plane disappear and hard to search for it, is to gently land the aircraft on water and let it sink. so that the debris field will be minimal.

To prevent people from escaping from a gentle landing plane on water, all you need to do it land upside down on water.
How?
-When the plane is upside down, it will be a lot more difficult  to reach your life jacket once you fell out from the seat and landed on the cabin ceiling. (life jacket will be 6 feet above)
- The door will be pushed close with the water pressure.
Even if the door does open and life raft is deployed, the sea water will be flowing in and push you away from the door.
As the the plane sunk further, the deflated door life raft will bend toward the belly due to buoyancy. It is hard to pull the detaching cord at the wrong angle.

Even so. it is very hard to land or even fly a plane upside down due to various of reason, such as oil pressure, fuel pump failure etc, the plane can only fly invert for a short period of time. it requires a lot of skills and muscle power to battle with the york.

on second thought, may be that is what the flight simulator is for, to practice invert flying.