The phrase flotation device is normally heard in airline and boating safety demonstrations, referring to anything designed to keep a person afloat in water. As a short isolated sound online, it lost that serious context and became a random meme insert, shared on soundboards for its deadpan delivery. Creators reuse it in pool, beach and gaming edits where the contrast between an official sounding label and a silly visual creates the joke, and its one second length makes it easy to drop into short form videos.