Australia already has a deep-sea survey ship there that it chartered to map the ocean floor in the area, the Fugro Equator, which is designed to withstand the towering waves and powerful storms that sometimes move through the area, 1,000 miles west of Perth. China has also sent a deep-sea survey vessel, the Zhu Kezhen, although Angus Houston, the Australian official overseeing the search, said in a telephone interview last month that the Chinese vessel was less specialized for working in heavy seas.

Australia stopped accepting bids last week for a 60 million Australian dollar, or $56 million, contract for up to three towed submersibles to spend as long as a year scanning the ocean floor with sonar for debris from the plane. The Australian Transport Safety Bureau has not yet chosen a winner for the contract.

Deep-sea submersibles are more reliable if they are towed fairly close to the ocean floor — sometimes as little as 100 feet from the bottom. But the submersibles can be wrecked if towed into a cliff or other seafloor feature. So the first step has been to map the seafloor in considerable detail for possible obstructions in the planned paths of the submersibles.

Martin Dolan, the chief commissioner of the bureau, said in an email reply to questions that Malaysia’s announcement on Sunday was in addition to Australia’s previously disclosed plans.