Concrete sidewalks, patios, sundecks, and grouted rocks can hide sink holes that form over time due to erosion and liquefaction of soils and substrate in yards behind shoreline armoring. In this case, a large cavity (13 feet deep x 30 feet long x 20 feet wide) formed underneath a rock revetment that extended into the rear yard, unseen until a small hole formed in the midst of the rear yard. Shortly thereafter, the former concrete patio and deck that held lounge chairs and picnic tables behind the revetment began to crack and collapse. Temporary stabilization methods allowed for a full repair from behind the revetment to be made and allowed the revetment to serve as a buffer to waves and storm surge. The resulting repair allows the revetment to continue to function and removed hardscape so that any change or settling would be apparent and can be remedied expediently.