Yes. You have to be searching the area where the plane crashed though. So far they have only searched the area where the plane did not crash. Uncertainty in the final minutes of flight have contributed to making the job of locating any wreckage very difficult. The ocean is large and deep and finding something as small as a passenger jet is hard unless you can narrow the search area.

Interesting idea, though I suspect a ship of that size didn’t break up as much as MH370 probably did. This would make detection harder since the remaining pieces would be much smaller.

They've used multibeam sonars among other types of sonars, without success.

https://www.youtube.com/watch?v=MOjVq5szAoU

The range of sonars is quite limited and the ocean is huge. There's really no point in searching unless you have a good starting point.