An urgent appeal has been broadcast to any ships in the Pacific Ocean to look out for an Australian man who fell off a cruise ship bound for Hawaii.
The man went overboard on the Quantum of the Seas at about 11pm local time (early Wednesday night AEST), about 1400km south of the Hawaiian islands.
9News understands witnesses saw the man fall from the top 15th deck.
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The US Coast Guard has issued an Urgent Marine Information Broadcast – a widespread radio message to alert ships in the area to a distress situation – to all vessels in the Pacific Ocean, south of Hawaii, to help look for the man.
Coast Guards have been searching the site with a C-130 Hercules for the missing man to no avail so far.
"They were able to cast out a few life rings," US Coast Guard Ryan Fisher said.
"Just so if he was in the vicinity in the water he could be able to grab onto them."
Passenger Susan Whittington noted there was "quite a large swell" overnight making it "almost impossible" for the search.
After six hours of searching, the aircraft was forced to run back to Hawaii to refuel.
The authority confirmed the aircraft will continue searching for the missing man at first light.
"If they are unable to locate him today the plan is to continue the search tomorrow as well," Fisher said.
The Coast Guard has also put out a call to the US Navy for aid.
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Passengers were woken by the PA system calling "oscar, oscar, oscar" – the ship's code for man overboard.
They were then asked to go back to their rooms and make sure all their travelling party was accounted for, while bright lights swept the water to search for the reported missing passengers.
About 90 minutes later, the passengers were told they could leave their rooms.
Passenger Georgina Thompson said she and her husband were in bed when they heard the alert call.
"There were lights, you know, the big lights shining on the ocean," she told Today.
"And also there were a couple of boats out there in the water."
Passengers are shocked by the ordeal, recounting a "sombre" mood on board the ship as it continues to its destination.
"It's a shocking situation to be in," Whittington said.
Thompson said it was "very sombre, very sombre".
The cruise ship, operated by Royal Caribbean Cruises, has been at sea for 15 days after visiting Tahiti.
The passengers on board are due to stop at Kona in Hawaii for a day on shore then the cruise will continue on its final stop in Honolulu.
It departed Brisbane on April 12.
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The Quantum of the Seas has resumed its course for Kona on Hawaii's Big Island.
"While on its trans-pacific sailing, a guest onboard Quantum of the Seas went overboard," Royal Caribbean said in a statement to 9news.com.au.
"The ship's crew immediately launched a search and rescue operation and is working closely with local authorities.
"Quantum of the Seas departed Brisbane on April 12 and is scheduled to arrive in Honolulu (on) April 28."
A Department of Foreign Affairs spokesperson said it is ready to help the family of the man who fell overboard.
"The Australian Consulate-General in Honolulu is working closely with local authorities," the spokesperson said.
"We acknowledge the ongoing distress for the man's family and loved ones."
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