由於其獨特的地理、歷史和文化，坪洲60%的沿海地區未被破壞。 可以找到不同的生物和海鳥，這裡的一些物種在香港很少見。 中華白海豚和河豚是附近海域的常客。
中華白海豚（Chinese white dolphins）
Uniquely, the population along the Chinese coast has pink skin, and the pink colour originates not from a pigment, but from blood vessels which were overdeveloped for body temp. control. These dolphins can live up to 40 years.
長江江豚（Yangtze finless porpoise）
The finless porpoises are the only porpoises to lack a true dorsal fin, the forehead is unusually steep compared with those of other porpoises
黃海馬（Yellow sea horse）
Sea horse use their dorsal (back) fins for propulsion and their flexible tails for cling to seagrass and other objects. They can change colour patterns to camouflage themselves and as courtship displays.
Commonly found on Hong Kong rocky coastal area, the large speciment reached up to 4 to 5 cm long. It is conical in shape with various colour and spotty radial lines
奇頓 （Liolophura japonica）
There are little researches on Chiton despite several different kinds were found. Only one or two species were identified. The lenght is about 6 cm for the larger kind. They live on the rocks exposed to low tide, it attached itself tightly on rock surface makes it difficult to distinguish from the background
根據土木工程拓展署和漁農自然護理署，坪洲周圍有 40 多種珊瑚。 其中一些在下面，