They are indeed searching and are now well on with the laborious mapping process of the area of sea bed of greatest interest.
[urlhttp://www.bbc.co.uk/news/world-asia-29378953[/url
This sort of thing:
The resolution is far too co to pick up something as small as an aircraft, but the mapping wasn't done for that reason, it was to plot courses to drag the detection equipment, without crashing into obstructions etc. Apparently, before this, we had better maps of Mars than of this area of sea bed, and the mountains on it are said to make the Himalayas "look like foothills" so the scale of the challenge is literally and mind-bogglingly enormous.