Whatever three men in a boat can do, two girls in a canoe can do better.
So claim Lindsay Dean and Heather Rand who aim to paddle from the source of the Thames to the sea.
They plan to take about a week to do the 150-mile journey.
Their feat will raise money for two autistic children in Watlington that they help care for.
The cash will send them to the Autism Treatment Center of America which, it is hoped, will help them cope better with the condition.
Lindsay and Heather, both 25, live at Watlington Hill Farm, Christmas Common, and both went to school at Watlington Primary and Gillotts School, Henley.
Neither Lindsay or Heather, who both work in caring for people with learning difficulties and autism, have done long-distance canoeing before.
Heather said: "We hope to raise more than £1,000 for the Laura and Stevie Fund to send Laura and Stevie Bannister, aged six and four respectively, to the treatment centre."
They will paddle from Ashton Keynes in the Cotswolds to Teddington Lock.
"People have called us inspired, intrepid - and insane," said Heather.
The pair are currently doing capsize practice in a swimming pool to be able to cope if the boat should turn over.
Anyone wishing to help sponsor their mission, should log on at the website www.source2sea.wordpress.com
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