There have been a number of speculations about breakup of the fuselage at the point of impact with the sea surface, or whether the aircraft would have remained largely intact if it had not broken up prior to hitting the sea. It is possible to do some ball park calculations that help understand the impact conditions. If the aircraft was descending at 5000 feet per minute, and impacted the sea in a near level attitude, and if the floor area containing the seat mountings in the fuselage area came to a halt uniformly in a distance of 2.5 metres vertically then one can work out the deceleration. Using very basic mechanics the deceleration is the square of the speed divided by twice the deceleration distance. Converting the initial vertical speed to metres per second gives 25m/s, and this leads to a deceleration of a little over 12G. It is quite possible that the deceleration happened in rather less than 2.5 metres and if it was 1 metre this gives deceleration loads of 30G. That is unlikely to be survivable. In addition this implies that the forces on component parts during impact are over ten times the normal forces under 1G loading. Hence deformation and failure of any parts of the structure are highly likely.
Given this kind of consideration it is not surprising that the most likely outcome is to find separated sections of the aircraft. The analysis of the debris field would of course need to include some estimates of the effect of sea currents both during the descent from the surface as well as post accident strong currents in the area. It is positive news today that the tail section has now been lifted from the sea onto a ship.