Four specialists from the air accident investigation bureau were ready to be deployed with two sets of detectors as soon as Indonesian authorities choose to activate them, the Civil Aviation Authority of Singapore said.
Officials said the hydro phones should be able to pick up the signal coming from the underwater beacon of the plane's flight recorder.
Specialists would then triangulate the rough position, so that divers or autonomous underwater vehicles could be deployed to search for the wreckage.
The plane is presumed to have crashed in the Java Sea after it disappeared from radar shortly after takeoff from Surabaya, Indonesia.
Flight QZ8501 was en route to Singapore with 162 passengers and crew, mostly Indonesians.