Yes, that is literally exactly what you need to do! However, make sure that your 6 IV Ditto is holding a Destiny Knot, and obviously the Adamant, hidden ability, Dive Ball, Female Carvanha must be holding an Everstone when breeding it with the Ditto. Also remember that the Dive Ball can only be passed down by a female Pokémon, even when breeding with a Ditto, so when breeding when you replace the Carvanha with a Carvanha with better IVs make sure that it is a female you replace it with.