One is -sub An example if a word with the directional prefix -sub is submarine How it changes the root word (marine) is, marine means: of, found in, or produced by the sea . Submarine means:<span>a warship with a streamlined hull designed to
operate completely submerged in the sea for long periods, equipped with
an internal store of air and a periscope and typically armed with
torpedoes and/or missiles So marine has to do with a person, while submarine has to do with a warship
