A world renowned surfer is planning a marathon challenge with a difference - paddling from the north coast of Ireland to Scotland.

Al Mennie, who has ridden some of the largest waves on record, is to steer a 20ft board 25 miles along the fringes of the North Atlantic.

Freezing conditions and fast tidal currents are the biggest threats to the surfer's chances of success.

"The two biggest challenges are the cold, nothing like this has been done this far north and at this time of year. The wind chill will be a big factor," he said. "Then there's also the tidal streams pulling you one way and then the next."

Mennie will use a stand-up paddle board as he charts a route skirting the North Channel from the Giant's Causeway to the Isle of Islay. The endurance test, expected to take eight hours, is being lined up for late March or early April and is based on similar stamina-sapping paddle races between islands in Hawaii.

"I chose this route because the distance matches one of the crossings the Hawaiians do in sun cream and board shorts. There was a shorter 12-mile route but I wanted more of a challenge," he said.

"I will be wearing a 6mm wetsuit and crossing one of the most dangerous stretches of water around the Irish coast known for its extremely deadly currents as the Irish Sea tides drain around Rathlin Island."

Water temperatures will be around 10-11C but the air temperatures could fall to about 5C depending on wind directions and strength off the Atlantic.

Mennie will be joined on the trip by a support boat which will help him navigate a straight course as swells and currents push him off course.

The charity endurance test will raise money for the Northern Ireland Chest Heart and Stroke organisation.