The Confederate Marine Corp was very small. They operated sometimes within both the army and the navy. For instance, serving ashore to place guns at Drewry Bluff and manning them also. Also serving at sea at the Battle of Mobile Bay. Captain Reuben T. Thom, Jr. was OIC for the guns of the CSS Virginia during the battle with the USN Monitor. He also served at Drewry's Bluff and at Mobile Bay.
There are people still interested in the Confederate Marine Corp. You may have to search on the general name and see who has a URL for that. I would bet thee is a re-enactor group.