More than 2,300 fabric and rubber ducks have been discovered in 56 countries over the past eight months, many with money and a note attached.

Although the note directed owners to The Little Yellow Duck Project's website, there was no information as to who was behind the campaign. The mystery was solved on Tuesday, when the women involved revealed themselves.

Ann Rowcliff and Emma Harris of Peterborough, Cambridegeshire came up with the idea after the death of Clare Cruickshank – Rowcliff's daughter and Harris' best friend. Cruickshank died on April 15, 2013 at the age of 26 from cystic fibrosis after a donor could not be found for a lung transplant.

Cruickshank asked that her own organs be donated upon her death, and her corneas were placed in two strangers. Rowcliff and Harris took their loved one's message of organ donation and decided to spread it through the Little Yellow Duck Project.

The campaign began in their hometown, where they would knit or crochet ducks and leave them for others to find. The random act of kindness quickly caught on, and others began leaving ducks and adding cash—usually $15 to $80.

Ducks have been found in Australia, Peru, Japan, Nigeria, India, and other countries, along with a note reading "Hello. Please take me home. I was made with love just for you," and an invitation to visit the organisation's website.

Harris, who also has cystic fibrosis, described the significance of the campaign.

"The ducks ... carry a deeper message which is that some random acts of kindness can literally save people's lives through the gifts of blood, bone marrow, organ and tissue donation," she said.

The initiative is exactly what Cruickshank would have wanted, her mother said.

"Clare was dotty about yellow ducks, she would have loved it, she was fun loving," Rowcliff recounted. "The ducks are so reminiscent of Clare, she was so bubbly. They make me feel like a little bit of her is still here.

"We would quite like to conquer the world!" Rowcliff added in regards to the project's popularity. "That was what Clare always said when asked as a youngster what she wanted to do when she grew up."