Two men seriously injured when their helicopter crashed in shallow waters off the central Queensland coast have been saved after their luggage began washing up on a nearby beach, sparking a search and rescue operation.

Police said they started searching for what they initially thought was a capsized boat after eskies, luggage and fishing rods started washing up on beaches near Gladstone on Saturday afternoon.

Just after midnight, the RACQ Capricorn rescue helicopter found a Bell 206 JetRanger helicopter partially submerged off Curtis Island, and discovered two injured men, a 61-year-old from Scarborough, and a 56-year-old from Margate, lying on the beach.

They had been stranded, exposed to the elements with very little to eat and drink, for more than 36 hours, having crashed on Friday afternoon.

Senior Sergeant Robyn Taylor-Ward said the label on one of the men's bags may have saved their lives.

"A search of the luggage located a name and address and police were then able to speak to their family and it was at that point in time we realised that a helicopter was potentially missing," she said.

Senior Sergeant Taylor-Ward said the men were in serious conditions, both with back pain.

"They obviously rendered first aid and the men were then transported to Rockhampton Base Hospital," she said.

'We were expecting to find either nothing or bodies'

A critical care flight paramedic on board the rescue helicopter said he was surprised to find survivors given the condition of the crashed helicopter.

Queensland Ambulance Service's Andrew Busby said the helicopter was spotted in shallow waters on Curtis Island.

The rescuers landed nearby and he and a crewman went on foot to search the wreckage.

They came across the pilot, while the other man managed to make his way to the rescue helicopter by foot.

"What we found with survivors was certainly in my eyes totally unexpected given the wreckage and the location," Mr Busby said.

"It was a very, very difficult rescue in reference to poor light, rising tides, remote location and poor communication."