A relative in the Coast Guard described the amount and composition of the crap floating on the surface of the ocean, and trying to figure out what an object it is when a fishing boat out of Florida goes missing. He said if you are able to bring the stuff on deck, most of it is just garbage that could be from anywhere/anything-rarely is anything significant found right away.
That floating stuff in the Indian Ocean they are seeing from a distance-plane or ship-probably is everything from flood/tsunami trash to crash debris-takes awhile to sort it out...
Indian Ocean trash is estimate to be 20,000,000 tons ...
And stuff is known to float for years, decades, even centuries from time to time, spending unknown amounts of time unremarked, stuck in the same long endless current, or in doldrums. The Indian Ocean has lots of shipping, stuff lost from ships is probably at least as big a problem there as anywhere. Of course, this search is going on in a place where the plane never was, imho.