A self-contained, emergency marker for attaching to, and selectively ascending from, a scuba diver's buoyancy control device. A buoy portion is contained in an enclosure and is selectively released therefrom by an activating apparatus. A buoy inflates, escapes from a buoy sub-enclosure by buoyancy, and tethers a buoy cord out of a buoy cord sub-enclosure when a pull pin is released, causing an upper end of an arm to bias away from the buoy sub-enclosure, causing a lower end of the arm to pivot toward the buoy sub-enclosure, causing a pin to rise and puncture a CO₂ cartridge. The buoy has thereon a beeper and a flashing strobe light that electrically communicate with a battery interface that, in one embodiment is located in the buoy, and in another embodiment is located in the buoy cord sub-enclosure.