I was playing on a mates realm and was using a boat and got out of it to dove to a wrecked ship. As I got back to the surface, the boat wasn't there. Later on after I had to craft a new boat, I got out of it again and it vanished right in front of me. There was no drop or anything, and I couldn't destroy it if it were invisible. 

link to YT clip: https://youtu.be/_UqV01ghcPw