An attempt by a Channel swimmer to become the first person to complete a non-stop swim from Cuba to the US without a shark cage has ended after 11 hours due to a severe debilitating jellyfish sting.

Chloe McCardel, who has swum the Channel six times - two of them two-way swims - began the swim yesterday.

But she had to be taken out of the water and on to one of the support vessels. She will spend 24 hours recuperating in Key West before deciding on whether to attempt it again.

It had been thought the swim - covering more than 170 kilometres - would take around 60 hours.

Chloe was using advanced but ecologically-friendly shark deterrent technology, but she had said she would still need to avoid the population of jellyfish, which have an excruciating sting.

Among her support team was her husband Paul McQueeney, who has also swum the Channel, in 2009.

Chloe has attempted a three-way Channel swim in the past, but had to give up on the third leg and was taken to hospital.