I worked with a woman who did find a message in a bottle once. It was from a person who lived in Australia and they had launched their message during a cruise. My acquaintance had found the bottle while walking on the beach in Florida. She wrote to the author of the message and they were able to meet in person. It is something that I have thought about and considered what I would put into such a message.
I think I would give a very short description of my life and provide my address, both physical and email. I would love to be able to launch my message in the Ohio River where it passes my hometown of Wellsville, Ohio. I would hope that my message would be found by someone that would read it and respond in kind. What I would hope for is to begin a dialog by mail or email that would last for many years.