I love discoveries like this! I thought Bosnia and Herzegovina became landlocked after Crotia split from Yugoslavia, but according to Wikipedia:
Bosnia and Herzegovina is an almost landlocked country – it has a narrow coast at the Adriatic Sea, about 20 kilometres (12 miles) long surrounding the town of Neum.
Here’s a map of Bosnia and Herzegovina from OpenStreetMap, with Croatia to the left alongside the Adriatic Sea:
And here’s the lower part of the country, with its coast centred on Neum: