Police have partially identified a drowned diver as a foreign national while trying to retrieve about 50 kilograms of cocaine near the NSW Port of Newcastle.
The diver was found unconscious in the water and later died despite attempts to revive him.
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 spotted in the water about 9.30am on Monday by port officials, before police later found 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.
A second crime scene has also been established up the river where police believe more drugs had been stashed, a police spokesperson confirmed to AAP on Tuesday without quantifying the amount.
The dead man had sophisticated and expensive dive equipment, NSW Police Detective Superintendent Rob Critchlow said.
That included a "rebreather" apparatus that lets divers breathe underwater without the telltale bubbles of less sophisticated scuba equipment.
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 had been searching the Areti, ABF Acting Superintendent Tony Wheatley said.
The ABF screens all ships and their crew when they arrive in Newcastle, he says.
The crew has also been interviewed and the vessel likely will be allowed to leave the port in the next 24 hours.
There were simple reasons driving the import of drugs into Australia.
"Australian users are paying probably the highest rate for cocaine in the world," he said.
"Our message for anyone thinking of importing cocaine into Australia is that the risks are too high."
Det Supt Critchlow said the port had been under police scrutiny for some time.
"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."
If the 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 continued searching surrounding waters on Tuesday with help from Australian Border Force officers.
Drug traffickers have been using divers to retrieve shipments from the hulls of ships on and off for years.
Queensland University of Technology associate professor of justice Mark Lauchs told AAP drug gangs would use any technique they think would work.
He says drug traffickers might have a different idea about whether the risk is too high, because enforcement only addresses the supply of drugs, not the demand.
"If people have the money, they will just pay more money, attracting more sellers," he said.
Legalisation is not necessarily a solution either.
The high taxes a regulated drug market would inevitably attract would open new avenues for criminals to continue importing illegally, similar to what has happened as taxes on tobacco increased.
"They will move in to a different way of making money off the same product," he said.