Mr. Optimistic
Is everyone so sure that the orientation of the debris doesn't give more information ? If the fwd and aft ends of the a/c are subsequently found at either end of the debris trail, it would be a clincher wouldn't it ie (ie that the debris reflects heading at impact)?
I suspect you are being a bit 'optimistic' sir.
The bits on the bottom probably do reflect the orientation of the aircraft at impact, but not in the way you suggest.
For example, if the aircraft impacted in a N-S attitude and the wing tip navigation lights broke off neatly from the structure in comparable size lumps, you would find the green light fixture approximately one wing span to the east of the red light fixture and located roughly along the centerline of the wreckage pattern.
If the aircraft impacted in a E-W direction, you would find the two light fixtures north and south of the wreckage centerline, separated by approximately one wing span, and the line between the two fixtures would be approximately N-S. The displacement from the right edge of the wreckage field would be dependent on fall rate through the water column and initial position on the aircraft in both of the above examples
There is a dispersion factor as aluded to by JD-EE. The dispersion factor is essentially a bell shaped curve around the calculated bottom impact position (based on the integral of local current velocity over fall time) and the span of the dispersion is proportional to radius of curvature that an object describes in its hydrodynamic trip to the bottom. You also have to consider possibility of collisions between particle elements deflecting them away from their original trajectories through the water.
All and all, it is a bit daunting problem in locating components of interest, but not impossible. If you find an element of comparable mass and hydrodynamic drag to a component you wish to find, and if you have an idea of initial aircraft orientation, you can significantly reduce the area to search for a target item, but you need to have an idea if the item immediately began to sink or might have traveled before sinking.