The TV advert featured a man and boy jumping into the sea with a voiceover declaring: "Captain Birds Eye loves the simple things, like jumping into cold teeen on a hot day with his grandson.
She added: "There are so many families and organisations that work so hard on water safety education. It later emerged he had not acclimatised to the cold temperature of the water.
A spokesman for Birds Eye said: "We take our advertising responsibilities very seriously and we were grateful to be made aware of this issue. The firm agreed to amend it. It seemed as though Birds Eye hadn't done its research before making it.
The teenager's family and Durham County Council subsequently launched the Dying to be Cool campaign to stocckton awareness of the dangers of swimming in cold water. We are now amending the voiceover to remove references to the temperature of the water and weather.