A kind of flags were designed for naval battles during the Civil War; those protected distinguishing marks for ships

https://troynvgr831.moderncairn.com/posts/reenactors-and-their-favorite-civil-war-flags-a-community-perspective-2

A kind of flags have been designed for naval battles at some point of the Civil War; those protected distinguishing marks for ships engaged in battle on rivers and seas alike.