Mrs Cosgrove had always been terrified of her son's occupation, worrying every time a boat went down in Fiordland, Mrs Culling said.
"This has been hard on her."
Mr Cosgrove's son and daughter, Wade and Hayley, had been in close contact with their grandparents since the tragedy.
Mr Cosgrove retired from fishing two years ago to manage a pub in Dobson on the West Coast, but his passion for the sea brought him back to skipper the Governor for the last six months.
"He's always gone back to the sea. He has always had something about boats.
"He was a confident seaman.
"The sea takes, but it doesn't give."
The weather has hindered dramatically the search. The police dive squad has been unable to reach the wreckage with sonar equipment that would determine if the pair's bodies were still on the boat.
Mrs Culling said the family accepted the weather had played a leading role and understood the search and rescue team's inability to locate the pair.
"You can't do the impossible."
The police dive squad visited the site of the wreckage on Thursday and gained footage using a remote operated vehicle.
However, strong underwater sea currents meant the dive squad was only able to get closer shots of one side of the boat.
The boat is lying upright and intact on the sea floor and police will consult the navy's dive team to ascertain its availability and the viability of using its resources to reach the wreckage.
The navy has the capability to dive to lower depths using a compression chamber.
Mrs Culling said the family would hold a memorial service for Mr Cosgrove soon.