None of the 80 passengers and 43 crew aboard the Australian-registered Coral Adventurer were reported injured when it hit a reef off the Finschaffen Coast, east of the PNG city of Lae early on Saturday.
The cruise has been ended early and passengers will be flown out of PNG on a charter.
The grounding follows a previous mishap involving the Cairns-based vessel on October 25 when an elderly female passenger died after allegedly being left behind on Lizard Island in far north Queensland.
An Australian Transport Safety Bureau (ATSB) investigation is under way into the PNG grounding, with the Australian Maritime Safety Authority also involved.
ATSB Chief Commissioner Angus Mitchell said the bureau was not involved in the recovery operation but continued to monitor it as part of its investigation.
When able to, bureau investigators would board the ship to conduct interviews and collect evidence and data, he said in a statement on Monday.
As reported to the bureau the grounded ship was heeled over about six degrees to port and initial efforts to refloat it using its own engines were unsuccessful.
The ship's operators, the NRMA-owned Coral Expeditions, have engaged a towage provider to help refloat the ship, with those efforts still under way on Monday.
"The extent of any damage to the ship's hull is not known but water ingress is not reported," Mr Mitchell said.
The ship's voyage data recorder had been quarantined and investigators were collecting ship tracking data, weather information and crew, operator and maintenance records.
A Coral Expeditions spokesperson said initial inspections indicated no damage to the vessel, with further inspections to be conducted once the vessel was refloated.Â
"Acknowledging that we have not been able to deliver the exceptional experience expected by our guests on this occasion, Coral Expeditions has decided to end the tour," they told AAP in a statement on Monday.
The company confirmed no one had been injured and all passengers would be flown out of PNG on a charter flight.
After the death of 80-year-old passenger Suzanne Rees in October, the Australian Maritime Safety Authority launched an investigation with head count practices and staffing levels under scrutiny.
Ms Rees had been hiking on Lizard Island with fellow passengers but broke off from the group after feeling unwell.
She never returned to the ship, which left the island but returned hours later once the crew realised Ms Rees was missing.
Rescue services recovered her body the next day and the rest of the cruise was cancelled.
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