Volunteers on Inchkeith came across the bottle while helping to clean up litter on the island.
The schoolboy, whose has been identified only as Jamie, was a pupil at a school more than 50 miles away in Berwick.
In the message, the boy explains that he is studying coasts and waves, and requests that the note be returned to his home address.
The Forth Estuary Forum is trying to contact him to let him know where and when his bottle was found.
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