Abstract: This invention concerns a water skier warning flag system of the type wherein the slackening of the tow rope causes a warning flag at the transom of the ski boat to be raised. A mechanical device mounted on the rear of the transom of a ski boat includes a lever having a normally vertical long lever arm for holding a longitudinally-mounted (normally vertical) standard of a warning flag; and this long lever arm also has a connection point to a ski tow line. The other (short) lever arm is urged by a compression spring to maintain the long lever arm vertical. When a skier is skiing, the tension on the tow line pulls the long lever arm down to horizontal against the pressure of the compression spring; and when the tow line goes slack, the spring pressure returns the long lever arm to vertical.