A tight-knit New South Wales community is in shock at the disappearance of a local paramedic and his girlfriend who went missing at sea after going overboard on a cruise ship.

Police have called off the search for the couple, who had been holidaying with family on the 10-day Carnival cruise.

Paul Rossington and Kristen Schroder, who were from Barraba in north-west NSW, were reported missing yesterday morning when the ship docked at Circular Quay in Sydney.

Police looked at CCTV which showed them going overboard on Wednesday night.

An air and sea search scoured 500 square nautical miles off the Forster coast where the pair went overboard. Local marine rescue have also alerted passing ships to keep an eye out for the couple.

Detective Superintendant Mark Hutchings says weather conditions and the medical health of the couple strengthened rescue hopes, but the pair went overboard more than 40 hours ago.

"It has been a long time since this incident occurred and whilst we hold out some hope, the hope is fading," he said.

Earlier today, police said it was unclear whether the pair jumped or fell.

Sorry, this video has expired Police still hope to find a couple who have been missing at sea for almost two days.

Carnival chief executive Ann Sherry has defended the ship's safety and security measures and says the gap in time from when the couple went overboard to when crew realised is because no-one saw the incident.

"The issue of the gap in the timing, it partly goes to a man overboard protocol," she said.

"We didn't realise the couple were missing until the disembarkation."

Authorities have been able to pinpoint a search location thanks to the CCTV footage.

But Ms Sherry says not all CCTV footage is monitored all the time.

Kristen Schroder and Paul Rossington ( Twitter )

"CCTV is monitored, but not every camera is monitored," she said.

"At that time of night, it was the last night of a cruise. Virtually everybody else was in the public spaces on the ship and they're the areas that we focus on at those times."

Ms Sherry has rejected claims that incidents like this have been common.

"I've been in this role for six years, in that time we've had two similar incidents, both of which were tragic, both of which had no suggestion of criminal activity or safety and security issues," she said.

She says the company has invested hugely in onboard safety monitoring.

"We can see exactly what's going on in most parts of the ship at most times," she said.

"There is also a balance of course around privacy - we don't watch what people are doing in their private spaces - but we are keen to know exactly what's happening around the sides of the ship."

'Shocking news'

Barraba resident Paula McIvor says it is devastating news.

"It's very sad in Barraba. The community is very, very saddened," she said.

"We're a very tight-knit little community here. We all know each other and we're very shocked by the news.

"We feel for all the relatives and family of these people."

Another local resident, John Bishton, says the 30-year-old paramedic is well-known and well-liked.

"He's a consummate professional," he said.

The search stretches from Sydney Harbour up the coast to Newcastle, following the track of the cruise ship.

Carnival Cruise Lines spokesman Peter Taylor says the company is working closely with police.

"We have naturally been concerned since we became aware that two passengers were missing from Carnival Spirit and our thoughts are clearly with their families at this difficult time," Mr Taylor said.

"We are working closely with NSW Police and assisting them in their inquiries."

Out of respect for the families of the missing passengers, he says the company will not be making any further comment on the matter.