Until now experts had been concentrating on mapping the seabed in the southern Indian Ocean search zone where the plane carrying 239 people is thought to have crashed in March.
The Malaysian-contracted GO Phoenix vessel has now arrived in the area and begun its work scanning the ocean floor for the jet, the Australian Transport Safety Bureau (ATSB) said.
"The vessel GO Phoenix, with equipment and experts provided by Phoenix International, has arrived in the search area in the southern Indian Ocean, and commenced underwater search operations," the bureau said in a statement.
Australia has been spearheading the hunt for the plane which is believed to have hit the ocean after mysteriously diverting off-course from Kuala Lumpur to Beijing and running out of fuel.
The search for MH370 has been frustrated by a lack of solid information about the jet's final hours and the vast and largely unexplored area in which it is presumed to have crashed.