It had been at sea for 28 years before it was discovered by a kite surfer cleaning the beach.
The note reads: "Mary, you really are a great person. I hope we can keep in correspondence. I said I would write. Your friend always, Jonathon, Nova Scotia, 1985."
Matea Medak Rezic, a 23-year-old surfer, found the message and nearly discarded the bottle before realizing something was inside said a Croatian newspaper.
There is no indication yet as to who the people in the letter are, just that they are from Nova Scotia, Canada, about 3000 miles away.
That means the bottle must have floated across the Atlantic and half the Mediterranean before entering the Adriatic sea.
Rezik posted a photo of the letter on her Facebook page to see if Mary and Jonathon could be found - if they want to be found.