A sort of flags have been designed for naval battles all through the Civil War; these incorporated distinguishing marks for ships

https://martiniyix278.unionquill.com/posts/flags-of-honor-the-symbolism-behind-civil-war-colors-and-emblems-3

A form of flags have been designed for naval battles in the time of the Civil War; those included distinguishing marks for ships engaged in combat on rivers and seas alike.