Looking at AIS (marine traffic), there seems to be frequent if not a great amount of traffic in or near the search areas at any one time, not including the vessels involved in the current search. I assume this means that the area is fairly close to some designated shipping lanes. Would be interesting to have historical data as you can with FR24, just to see what was in the general area around the early morning of 8/3.
I'm sure that someone will remind me of the vast expanse of the area involved and the chances of a vessel being remotely close are slim, but you never know.
BTW I'm only talking about seeing or hearing something, not being involved in any way....