Air resistance can cause low density objects to hit Terminal Velocity. Even a high mass object that has a shape that impedes air movement can hit terminal velocity. A large block of Styrofoam dropped from a tall building will not reach freefall velocity because it has too much drag as it falls. It won't stay buoyant like a soap bubble, but it also won't fall as quickly as a large rock from dropped the same height. In a vacuum, this is obviously not the case (feather and hammer).