Bottled Communication

It is very common, in the stories and novels, a shipwreck lost in the immensity of the ocean throwing a bottle to the sea containing some distress message. Days or weeks later, a ship sees the bottle and the shipwreck is saved.
For this is not just fantasy. Many bottles have already been used as a means of communication. Courier bottles not only saved human lives, but provided important scientific information about sea currents.
Although it is a rudimentary and somewhat uncertain means of sending messages, a bottle thrown into a sea current can travel about 200 kilometers per day.
The longest voyage (recorded) made by a bottle was started in 1929 on the Kerguelen Islands by a German scientific expedition. The bottle reached the southern tip of the American continent, doubled Cape Horn, crossed the South Atlantic, and returned to the Indian, completing a circumnavigation of the globe. It traveled about 16 800 nautical miles (30 000 km).

And if you're lost on a desert island! What would the message put in the bottle?