Open-water swimmer Beth French wants to swim across seven of the world's most dangerous sea-channels - an extreme challenge called Oceans Seven - and do it in record time: within one year.

Driven to set an example for her autistic son and by her battle with a life-long debilitating illness, Beth travels to far-flung corners of the world confronting jellyfish, sharks, wild weather, hypothermia and mind-numbing fatigue.

But, in an unpredictable and emotional climax, Beth’s burning desire to conquer the open sea comes into heart-rending conflict with a mother’s dreams for her son.