When you go out sailing or fishing in any large body of water (not just the ocean, but lakes or huge rivers, too), you might have the chance to see some really neat stuff. People leave random things out in the water all the time. Though, finding something like a message in a bottle still seems pretty rare.
A Reddit user by the name of Gregphish shared a picture of a message bottle he found while fishing in the Patuxent river off Solomons Island in Maryland, only it was a lot more than one message! In the picture, which he posted to the Mildly Interesting Reddit community, you can clearly see a bunch of messages!