The plane would have to be tumbled along the bottom to be broken up that badly. For starters, even with a more dense fluid, that would take a substantial current. Additionally, the plane would not be found where it sank, but some distance from there if it had been tumbled that way. Smaller and less dense fragments would be transported farther from the site and be less likely to be recovered. Surface currents do not equal the current at depth.
One more question. Where is the engine in the tangle on board the salvage vessel? Seems like that would be a priority considering that had been documented as the part of the aircraft that failed leading to the ditching.