Ronan Keating has told of his battle with giant jellyfish while swimming the Irish Sea in a marathon fundraising effort.

The charity relay for Cancer Research UK sees famous names swim the 56 nautical miles (65 land miles) from Holyhead in Anglesey, North Wales, to Dublin.

Ronan, 34, was first off the slipway in his wet suit and flippers on Tuesday night, followed by TV presenter Jenny Frost, who then handed over to Strictly star Pamela Stephenson.

Gadget Show host Jason Bradbury and Olympic medallist swimmer Steve Parry are also taking part.

Speaking during a break, Ronan said he was mostly spending his hour-long stints swallowing sea water and avoiding ‘alien-like’ jellyfish.

“I’m not one of the advanced swimmers so I’m concentrating on my swimming, my breathing and keeping my body moving,” he added.

“We were warned about the Lion’s Mane jellyfish, but there are hundreds and it’s frightening when they are right there sitting in front of you.

“You gasp and lose your breath, but you’ve just got to keep moving. Thank God we haven’t seen any sharks, I’m very happy about that.”

Tidal variations mean the swimmers have to zig-zag across the waters and could end up covering a distance of up to 70 nautical miles (81 land miles).

Ronan added: “We’re pretty much halfway across the Irish Sea now.”