Outdoor Swimming Society in bid to swim River Thames
A branch of the Outdoor Swimming Society is attempting to swim nearly all of the River Thames.
Swimmers will start in Gloucestershire and go through Wiltshire, Oxfordshire, Berkshire, Buckinghamshire, Surrey, Essex and Kent.
The trip by the society's Oxfordshire branch is due to take a couple of years as they will only swim at weekends.
In 2006 Lewis Pugh of South Africa became the first recorded person to swim the length of the river.
The total length of the Thames is 215 miles (346km).
It is not possible to swim the part of the route from the source near Kemble in Gloucestershire to Cricklade in Wiltshire because it is too shallow.
On Good Friday the society members will walk that part of their journey and the following weekend they will swim or wade down to Water Eaton in Oxfordshire.
Eventually they will make it to Teddington in London, which marks the end of the fresh water Thames. After that they will need permission from the Port of London authority to continue.
Sefryn Penrose, from the society, said the group swam all year but in the winter months did not make much progress.
She added: "The coldest month last year was December when it was around a degree or two and we only managed about 400 metres.
"That was difficult and painful. Usually there is just a little shock and then you're over it, but in December you don't get over it."
The Oxfordshire branch of the Outdoor Swimming Society is open to all ages and abilities and always welcomes new members.
"It gives you a real sense of euphoria and it really improves your mood and that lasts all day," said Ms Penrose.