A KEWARRA Beach couple have made a lucky escape after their large fibreglass vessel sank 38km off the coast of Cairns on Saturday.

The male and female on-board were unable to access life jackets and the EPIRB after the anchor rope allegedly became entangled in the outboard motor of the vessel about 9.50pm on Saturday, causing the stern of the boat to face the swell.

Before long waves swamped the 5.2m fibreglass vessel forcing the pair into the water

Acting Sergeant Heidi Marek said one of the passengers was able to screenshot GPS coordinates on their mobile phone, which were conveyed to Water Police officers who rapidly activated a search and rescue operation.

"Following an immediate response to the urgent situation, the two adults were located by the Water Police about 11.05pm treading water and clinging to an anchor float that they were able to retrieve prior to the vessel sinking," she said.

"One of the passengers used the torch on their mobile phone to guide police to their exact location.

"Both adults were exhausted but otherwise in good health."

The pair were examined by emergency services but didn't require further medical attention.

Originally published as Pair's quick thinking after boat sinks at Arlington Reef