It’s easy to send out a message in a bottle, but it’s hard to get anyone to notice it. In 1922 Hannah Rosenblatt sought to remedy this by adding a bell:
It will be seen that I provide a carrier that will positively float until washed upon shore or picked up by a passing boat. The peculiar shape of the support in combination with the bell assures the attraction of attention which is a very important feature of my invention.
Rosenblatt lived in the Philippines — perhaps there’s a story behind this.