The Shengsi Islands are geographically part of and located in the mouth of the Yangtze River . They comprise 394 islands, each with an area larger than 500 m?, but of which just 18 are inhabitable. The largest island is Sijiao Island with an area of 21.2 km2>.
The area is administrated by Shengsi County in the Zhoushan Prefecture . The islands have subtropical climate, with yearly average temperature of 15.8 °C. The area is also notable as touristic destination and fishery area that attracts more than 100,000 fishermen every winter.