The suggestion by James7 that a large jet with underslung engines could ditch in the middle of an ocean, come to rest, and then sink two or three miles to the sea bed, while remaining completely intact, is implausible.
Even if the ditching was flown by a practised pilot, and with all high-lift devices available, it is more than likely that the engines and pylons would be torn off, as well as all or substantial parts of the slats, flaps and elevators. Even if the engines remained attached, the fan cowlings would probably be ripped off. Apart from the engines themselves, most of these large items are made of composite material, and would float.
If the ditching was uncontrolled, it is likely to have been with a clean wing at a minimum of 200 knots, and the wings are unlikely to have been level (even if the surface of the water was). The chances of the a/c landing flat to the water and parallel to the swell are remote, so the a/c would be likely to cartwheel - like the Ethiopian Airlines B767 did many years ago - and break up. In that event, the fin would almost certainly detach and float, as-per AF447, together with an enormous amount of other debris.
The absence of any wreckage recovery is deeply puzzling, IMO. I'm not aware of any major storms in the search area in the interim, but I stand to be corrected. By now the search teams have had plenty of time to estimate the possible effects of current and wind on the movement of different types of weckage.