Techniques are disclosed for providing retractable control fins on an underwater vehicle. The retractable control fins can be extended away from a main hull portion of the underwater vehicle and retracted inwards to a stowage region within the hull portion to protect the fins from damage and reduce an overall outer diameter (e.g., in the case of a cylindrical body) of the underwater vehicle. In some embodiments, the control fins are folded inwards to reduce the vehicle diameter. In other embodiments, the control fins are pulled inwards using a rotating structure designed to slide the control fins through an opening and into an inner portion of the hull to reduce the vehicle diameter. The retraction of the fins through the various retraction mechanisms reduces the envelope diameter of the underwater vehicle.