For two decades Diego Makovac has made a trouble-free living fishing for sole in Piran Bay. But he now faces a flurry of Croatian and Slovenian patrol boats as the two countries fight over the water.

PORTOROŽ, Slovenia — My mom’s side of the family, the Tauchers, is Slovenian. This is partly why I went to Slovenia last year during the Christmas season. Some of you find this interesting while ...