Plane search goes underwater

With time running out to find the flight recorder of missing Malaysia Airlines flight MH370 Saturday's search was the most intensive so far.

The Australian navy vessel Ocean Shield has joined the hunt.

It's being used to tow specialist sonar equipment that could trace locator signals from the plane's black box flight recorder.

The ship's on a converging 240-kilometre course with a British vessel in the southern Indian Ocean.

Royal Australian Navy Commander James Lybrand says they're hoping for a result.

(SOUNDBITE)(English) ROYAL AUSTRALIAN NAVY COMMANDER JAMES LYBRAND SAYING:

"On board the Ocean Shield at the moment we're certainly doing all we can in the location we're at. We're running a series of parallel legs over best constructed location of MH370's last position."

Also taking part are 10 military aircraft, three civilian ones, and 11 ships.

A British nuclear submarine and a Malaysian frigate were also due to join the search.