Practical implication: If you are stranded on a desert island and you attempt to solicit a rescue by releasing a message in a bottle, you have about a 65% chance of a response (within ten years, I guess). In order to get that above 95%, you would need to release 3 or more bottles. 5 bottles gets you a 99.5% chance.
Of course, you'd better have a GPS device so that you can write down your coordinates on the message, or else you'd better hope the bottle turns up at an oceanography instutute that can trace the ocean currents back to where you're stranded.
Considering you can provide as many details on HOW you got stranded there (flight numbers, cruise ship name etc.) as possible and add details about WHERE you got stranded, I think that would help search&rescue to at least narrow it down... or maybe you are very lucky and the place has some pretty unique characteristics?
I think the biggest problem would be actually getting the people who find your message to turn it in to the police or so and then you got to hope they won't just throw it away or wouldn't even know where to forward the message to.
Of course, you'd better have a GPS device so that you can write down your coordinates on the message, or else you'd better hope the bottle turns up at an oceanography instutute that can trace the ocean currents back to where you're stranded.