The helicopter from 816 squadron at the Nowra-based Fleet Air Arm, believed to be call sign "Berserker", was onboard HMAS Anzac which responded to the emergency.

Last Thursday (May 13) the Indonesia authorities notified the Australian Maritime Safety Authority AMSA Response Centre that 35 metre commercial fishing vessel in trouble off the WA coast and required assistance.

Initially, it was believed there may have been up to 26 persons on board, however, that number was confirmed as 20.

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Early the next day, the Perth AMSA Challenger Jet conducted a sortie out to the vessel and dropped several life rafts.

The Australian Defence Force also assisted by providing two Royal Australian Air Force P-8A Poseidon maritime surveillance aircraft and one C-130J Hercules, who were also able to deploy life-rafts to the vessel.

The AMSA Response Centre issued a broadcast to shipping on Thursday evening.

Australian officials contacted the Indonesian company which owns the vessel and said there was no suggestion it was a people smuggling venture.

On Friday and again on Saturday night the Australian Defence Force deployed P-8A Poseidon aircraft to deliver life rafts to the 20 stranded fishermen who were clinging to their vessel.

Dramatic footage from the aircraft showed the fishermen huddled together in the bow of the ship which was taking water and being pounded by large waves.

The ADF worked closely with other aircraft coordinated by AMSA.

Royal Australian Navy frigate HMAS Anzac, which was hours off docking in Perth from a recent mission - with family members of the crew ready to greet them at the wharf, was diverted to the scene.

Saturday morning the Japanese fishing vessel Fukuseki Maru 15 arrived at the location and successfully transferred the 20 fishermen from the sinking boat to their own.

All 20 aboard the Indonesian vessel were rescued, with none reported lost.

On Saturday afternoon HMAS Anzac successfully received the 20 fishermen from the Japanese vessel via Anzac's sea boat.

The fishermen received medical support with one requiring urgent care and was to be transferred by Anzac's MH-60R helicopter to a Perth hospital when in range of the coast.

Anzac will then return the remaining fishermen to their home port in Bali with an expected arrival late next week.

AMSA Executive Director Response, Mark Morrow, said the successful rescue mission was a relief to all those involved.

"Saturday morning, the Japanese fishing vessel reached the Indonesian fishermen whose boat was sinking and was able to render assistance to those onboard," Mr Morrow said.

"Their quick response was instrumental to the success of this time sensitive mission.

"HMAS Anzac was then able to arrive with medical and interpreter support for the rescued fishermen.

"The successful saving of 20 lives at sea is an incredible achievement of which all responding authorities should be proud.

"We appreciate the assistance of the ADF and FV Fukuseki Maru 15 in this search and rescue mission."

Defence Minister Peter Dutton thanked the crew of HMAS Anzac as well as the aircrew who dropped essential items, which helped the Indonesian crew survive until their rescue.

"I also want to acknowledge the patience and good will of the families of Anzac's crew, who are now waiting longer to see their loved ones following a long deployment," Mr Dutton said.

"We will have your sailors back with you as soon as possible.

"Their efforts in bad weather and high sea state should make all Australians proud. They helped save 20 lives."