Two cousins who were blown out to sea paddle boarding off Ireland's west coast were found clinging to a buoy on a lobster pot after a 15-hour ordeal, media reports said.

The Irish Coast Guard said the women aged 17 and 23 were rescued on Thursday after being reported missing the previous evening, prompting an overnight air and sea search of Galway Bay. They survived heavy rain and strong winds without wetsuits, although they were wearing buoyancy aids, Barry Heskin from the RNLI lifeboat service told public broadcaster RTE.

A local fisherman eventually tracked down the pair 27 kilometres (17 miles) from where they were last seen, having set off with his 18-year-old son to find them, RTE reported. "They were waving their paddles up in the air, they had us spotted, well they were waving anyway and then we came alongside," fisherman Patrick Oliver told the broadcaster.

"They are weak and tired of course but they were sitting up and (we got) a little bit of chat out of them," he said, adding that he and his son had brought the cousins to an island where they were picked up by a helicopter and taken to hospital.

Their paddle boards were inflatable, which meant the wind would have pushed them out to sea quicker, a local coastguard boss also told RTE. Prime Minister Micheal Martin said he welcomed news of their rescue "very very warmly" and that it highlighted the work of emergency services and voluntary groups nationwide.