Mystery surrounds the identity of a dead diver and 50 kilograms of cocaine found floating in the water near the NSW Port of Newcastle.
Police have not yet identified the man, despite running him through various databases after he was found unconscious and later died.
They are investigating whether he was a drug mule linked to an international drug syndicate whose job was to retrieve the bricks of cocaine from a ship or the ocean floor.
He was found unconscious about 9.30am on Monday by port officials, before police later spotted a number of packages containing the white powder with an estimated street value of $20 million.
Police are investigating whether the drugs came from the nearby cargo ship Areti, a Marshall Islands vessel which arrived in Newcastle from Argentina on Sunday.
Two boats - a rubber dinghy and an aluminium runabout - were also seen near that ship on Sunday night.
The dead diver had sophisticated dive equipment, NSW Police Detective Superintendent Rob Critchlow said on Tuesday.
That included a "rebreather" apparatus that lets divers breathe underwater without the telltale bubbles of less sophisticated scuba equipment, which carry price tags that run into five figures.
Det Supt Critchlow has appealed for any dive shops that may have sold the equipment, or a Sharkskin brand wetsuit, to contact police.
Australian Border Force officers have been searching the Areti for the past 24 hours, ABF Acting Superintendent Tony Wheatley said.
The ABF screens all ships and their crew when they arrive in Newcastle, he said.
The crew has also been interviewed and the vessel likely will be allowed to leave the port in the next 24 hours.
The port has been under police scrutiny for some time, Det Supt Critchlow said.
"There have been some indications in the past of (outlaw criminal motorcycle gang) involvement around the docks," he said.
"It remains a point of risk ... and organised crime definitely look for weaknesses to target those ports."
Using divers to retrieve shipments from the hulls of ships has been used on and off by drug traffickers for years.
If the dead diver is linked to the drug shipment it's assumed he wasn't acting alone.
"These people have fled so it's quite disgusting that this man's been left to die regardless of what he was involved with," Det Supt Critchlow said.
Police divers will continue searching surrounding waters on Tuesday with help from Australian Border Force officers.
