The Fire and Rescue Service inshore lifeboat was sent inland to the Handois Reservoir after farmer Richard Leith saw the animals stuck up to their necks in the water.
They had fallen down a three-metre drop after wandering down a steep slope and getting through two fences.
They were from a group of six cows belonging to Mr Leith, who has 250 milking cows and rents land in St Lawrence from Jersey Water.
