The Island Barn Reservoir lies south of the River Thames in England at West Molesey and north of Lower Green, Esher.

The reservoir was named after Island Barn Farm, which previously existed on the site, and was completely surrounded by the rivers Ember and Mole.

[6] The reservoir allows some settlement of suspended solids; biological cleaning through exposure to sunlight; and provides a buffer storage volume to maintain capacity at times of low flow in the river.

In 2017 interlocking sheet piling 18.5 m long was driven vertically through the centre of the embankment into the London clay to stop the leakage.

Among many successful current and past members has been Fireball world champion and ISO designer John Caig and British Olympic, European Champion and World Cup sailor Nicola Groves.