Samples of encrusted Saccostrea cuccullata or rock oyster, indicated an age of around 7000 years old. This suggested that most of the present coastal area of Langkawi archipelago was submerged about 7000 years ago. Rock oysters can grow up to 20 cm long and are very common throughout the Indo-Pacific, Eastern Atlantic, and the Mediterranean. It is a bottom-dweller marine bivalve living at a depth range of about 0-5 m.
Tanjung Dendang Island is located in northeast of the Langkawi main island. It is an elongated island with north-south alignment. The island is composed of the Setul Formation. The northern part consists of the Middle Ordovician limestone, and the southern part comprises the Lower Silurian limestone. The two limestone members are separated by the Lower Silurian Detrital Member. The rocks are well-exposed at Cina Mati Bay.