A kind of flags were designed for naval battles all the way through the Civil War; these protected distinguishing marks for ships

https://zionitwe861.clearminster.com/posts/flags-of-honor-the-symbolism-behind-civil-war-colors-and-emblems-3

A number of flags had been designed for naval battles throughout the Civil War; those blanketed distinguishing marks for ships engaged in fight on rivers and seas alike.