Is this true When Admiral Horthy got his rank Croatia belonged to Hungary so it had a coast

Yes, that is true. Admiral Miklós Horthy was the Regent of Hungary from 1920 to 1944. During this time, Hungary was part of the Kingdom of Hungary, which existed as part of the Austro-Hungarian Empire until its dissolution after World War I in 1918. After the Treaty of Trianon in 1920, Hungary lost significant territory, including its coastline on the Adriatic Sea, which had belonged to it when it was part of the Austro-Hungarian Empire. However, before the treaty, Hungary did indeed have a coastline along the Adriatic Sea, specifically through the territory that included parts of modern-day Croatia. Thus, when Horthy held his rank and became the regent, Hungary did not have a sea coast, but the historical context of the Austro-Hungarian Empire included a coastline that belonged to Hungary prior to the territorial losses imposed by the Treaty of Trianon.