No, I’m not talking about the song by The Police. I’m talking about a real bottle that you can sent by mail!
A while ago I was in a museum and in the shop I found a plastic bottle with a blank sheet in it. I really like the whole idea of sending a letter in a bottle, so I bought one and sent it to myself since I didn’t knew if the bottle would survives the postal journey. And it did! After four days, the bottle and letter arrived in my mailbox in the same condition as I had sent!