Larger underwater vehicles may be required because of extreme depth.
An underwater drone searching for the missing Malaysia Airlines plane has been forced to resurface due to a technical problem - the second time its search has been interrupted.
The autonomous underwater vehicle, Bluefin-21, was forced to resurface to fix a technical issue, the Joint Agency Co-ordination Centre said.
While on Ocean Shield's deck, its data was downloaded and the vehicle was then redeployed to continue its underwater search for the plane, which was carrying 239 passengers and crew when it went missing more than five weeks ago.
Initial analysis of the data downloaded yesterday morning did not indicate any significant detections, the centre said.