Two scuba divers were plucked from the open ocean almost 24 hours after they went missing on a pleasure dive on Austrailia’s Great Barrier Reef.

The divers, 38-year-old Briton Richard Neely and American Allison Dalton, 40, were found shortly before 9am 7.8 nautical miles from where they had lost contact with their diving boat on Friday afternoon.

They were winched to safety after an 18 hour air rescue effort involving up to 12 aircraft and flown to a Queensland hospital where they are said to be in good spirits despite suffering from mild hypothermia.

Last night, police and emergency services used helicopters and fixed-wing aircraft equipped with search lights and infrared sensing equipment to search for the divers but were forced to call off the search.

At first light this morning the search continued with seven helicopters and three fixed wing aircraft. A rescue helicopter spotted the pair near the Whitsunday Islands off the Queensland's coast.

Police said the experienced divers surfaced yesterday afternoon around 200 metres from the dive boat but were unable to raise the crew.

They decided against fighting the strong current to conserve their energy, tying themselves to each other with a weight belt.

"They conserved energy throughout the evening and stayed as a pair awaiting rescue," Acting Superintendent Shane Chelepy of the Water Police said at a press conference in Brisbane today.

"From the debrief we have, these people said they did spot one of the search aircraft last night but were unable to attract its attention," Deputy Police Commissioner Ian Stewart said.

Following the search, attention has now turned to the dive boat operator, The Pacific Star, whose skipper was believed to have waited three hours until 5.30pm to alert emergency services to the missing divers.

"That issue will be investigated thoroughly, not only by Queensland Police but also by Workplace Health and Safety in a joint investigation," Mr Stewart said

"Obviously there were other divers with that vessel at the time so we will have to look into what happened with their recovery - whether they were back on the boat and what actions the captain took to commence the search.”

Attempts to contact the operator of The Pacific Star were unsuccessful today.

A similar incident occurred in 1998 when an American couple was left on the Great Barrier Reef by a dive operator at St Crispin Reef near Port Douglas.

The skipper of the dive boat was charged and later found not guilty of the manslaughter of Thomas and Eileen Lonergan after it was concluded by the coroner they had drowned or been killed by sharks.

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