A family in NSW is furious over alleged police "inaction" following the disappearance of their beloved grandfather feared to have gone overboard on a ferry in Manly.

Kenneth Hanes, 73, left his home around midday last Tuesday and hasn't been seen by family since.

His wife, Nola, logged into his Opal account on Thursday and discovered that Kenneth had boarded a bus on the day he left to Blacktown Railway Station.

His daughter, Fiona Crawford, believes that the local police hasn't done enough to find him.

"If a child went missing on the ferry from Manly to Circular Quay, would police wait three days to request information?" she said.

"It's soul destroying that we have no answers and there's just so much inaction and he's a human being. He's not a shift, he's not a case file number."

His family said that police acted too late in finally searching the harbour.

"It's so disappointing to think we treat our elderly like that," Ms Crawford said.

"My dad wasn't a doddery 73-year-old man with dementia that just flopped off the Manly ferry.

"He was a human being that went to Manly and got on public transport.

"He just deserves so much better than this."