Things float. Even things from an exploded plane and falling from 30? whatever thousand feet. Once debris is spotted and an estimate on its drift at least there will be a Ballaprk to play in for wreckage. Next will require a deep sea submersible which are available ...at a price. Im not sure of the depth in that part of the world, but I do think its way over my head. Another big problem, but today not something that cannot be done.
Black Boxes are a must but even they will only tell configuarion and telemtry at the time, not the cause.