A dog walker found the exotic creature which is native to rivers and swamps in southern parts of US in Urswick Tarn, near Ulverston on Monday.
Veterinary Surgeon Dr Dominic Moule said turtle which gives a nasty bite would likely have eaten through everything it was not rescued.
Parish councillor Denise Chamberion fished it out of water with a shopping basket and took it to vet.
Ms Chamberlan who lived in Florida saw a social media post about turtle and immediately recognised the species.
While it is not illegal to own alligator snapping turtles vets do not recommend keeping them as pets due their complicated needs.
“I suspect somebody has bought it and not realised what it is it has got too mega for them to look after or they can not afford to feed it”.
Ms Chamberlain went to retreive it with the assistant of residents.
She said ” I was anxious on two levels”.
“One was actually catching it without losing a finger but also what was I going to do with it?”
She wore three pairs of builders gloves and used a shopping basket to scoop the turtle out. She transported it to a large container with water from the tarn.
” Everybody rallied round to help” she added.