I found a message-in-a-bottle in 2013 which had been at sea for 7 years...
The bottle had been thrown off a container ship 200 nautical miles off the Orkney Islands on its way from Denmark to Greenland. The finder of the 'bottelpost' was to send a note to the sender with an address in North Eastern Jutland, Denmark.
In September 2016, I went to Denmark.
In advance of my trip, I sent him a note with my contact details telling him I would be in the area if he would like to team up for tea/drink/meal to let me know. I also included a map showing the location of the wreck of the 'Bottelpost Explorer'. I sent the package Registered Post.
On 7 November 2016, my package was returned to Ireland marked 'Unclaimed'.
An Post's on-line record of the map's journey from Ireland to Denmark and back.