This is one of the geographical oddities that I like so much. The smallest "island" in the world that is shared by 2 countries, Finland and Sweden, Market Reef is located right in the middle in the Gulf of Bothnia between Sweden and Finland. When Finland was occupied by Russia, Russia decided to build a light house over there. But by mistake, they did that on the wrong side, on the Swedish one. For many years, nobody cared much about this mistake. Only lately this mistake was corrected, which now results in a very funny redrawing of the border. In order that the light house now formally belongs again to the Finnish territory, the Fins had to cede part of their territory to Sweden.
Market Reef cannot simply be reached, no regular scheduled boat service will take you there. Rather, you have to charter a vessel, operating from Aland (details can be googled). In 2018 we paid 600 EUR for the total trip. It is even not guaranteed that when you are on Aland, that the trip will take place. All depends on the weather conditions. So, while I was lucky, it was the second or third attempt for others to reach Market.