A drain plug for a threaded opening in a fluid container that is particularly suited for transom drains in recreational boats. The plug has an externally threaded cylindrical body with a central channel and transverse openings to permit fluid to flow from the central channel out of the body of the plug. One end of the plug is flared and has a plurality of longitudinal slots that will allow the radial compression of the end when the plug is screwed into a threaded opening. In one embodiment, the radial compression of the end of the flared plug is limited by a ring that fits in an annular groove in the interior of the body in the central channel. In another embodiment, the external threads are tapered near the handle to provide a tight seal when the drain is fully closed. Another embodiment provides an o-ring to seal the drain plug when the drain is closed.