A style of flags had been designed for naval battles for the time of the Civil War; these incorporated distinguishing marks for ships
https://kylervbbv051.readspirex.com/posts/flags-as-historical-artifacts-insights-into-the-civil-war-era
A number of flags were designed for naval battles throughout the time of the Civil War; these blanketed distinguishing marks for ships engaged in struggle on rivers and seas alike.