Abstract: An anchor drift warning system includes an anchor indicating buoy and a reference buoy. Each buoy includes a floating housing, a light, a battery, solar powered battery recharger, and a spool. Radio signaling apparatus may be included to provide alarm indication aboard the vessel. A line retractably held in the spool of the indicating buoy is attached to the main anchor of the vessel. A line retractably held in the spool of the reference buoy is attached to its own anchor or to a weight. Both buoys are stowed proximate the anchor, and discharged into the water when the vessel main anchor is deployed. The reference buoy is substantially immobile upon deployment. The indicating buoy will move with the anchor, if the anchor has failed to be immobilized by solid engagement with the water bottom. Visual indication of this condition is provided by increasing distance between the indicating buoy and the reference buoy.