A form of flags have been designed for naval battles all through the Civil War; those included distinguishing marks for ships

https://shaneheqp027.slatecurrent.com/posts/from-cotton-to-canvas-the-materials-behind-civil-war-flags-2

A type of flags had been designed for naval battles for the time of the Civil War; those protected distinguishing marks for ships engaged in wrestle on rivers and seas alike.