Outdoor Swimming Society tries to swim the Thames
The Oxfordshire branch of the Outdoor Swimming Society is attempting to swim nearly the whole length of the River Thames.
Members will start in Gloucestershire and swim through Wiltshire, Oxfordshire, Berkshire, Buckinghamshire, Surrey, Essex and Kent.
Sefryn Penrose, from the society, said she expected the journey to take a couple of years, swimming at weekends.
In 2006 Lewis Pugh from South Africa became the first person to swim the length of the river.