What ship was Nimitz on during Battle of Midway?

nimitz wasn't on any naval vessel. he was in sick bay with a highly itching skin rash.

actually this is incorrect, it is true that Nimitz was not present, he was in Pearl Harbor. however he was not the one with dermatitis, Bull Halsey was the one down with the rash, Raymond Spruance actually took temporay command of Halsey's carrier group for him during the Midway campaign