Why can oysters stay attached to the same surface for life?

Oysters are able to remain attached to the same surface for their entire adult lives because they are sessile animals that undergo a process of cementation.12

After beginning life as free-swimming larvae, oysters eventually find a suitable hard substrate. Upon settling, they permanently attach themselves to this surface by cementing their shells to it. This transition marks the end of their mobile larval stage and the beginning of their sedentary adult life, during which they remain fixed to the substratum. Unlike other bivalves that may use proteinaceous byssal threads for anchorage, true oysters (family Ostreidae) rely on this cementation process to secure themselves to estuarine hard surfaces.3142