What is the only city-island country in the world?

Singapore, located in Southeast Asia, is a tropical city island country at the southernmost tip of the Malay Peninsula. It covers an area of ??647.5 square kilometers. It is adjacent to Malaysia across the Johor Strait to the north, connected to Johor Bahru in Malaysia by a causeway, and faces Indonesia across the Singapore Strait to the south.

Singapore has insufficient groundwater resources. Although the annual rainfall is as high as 2,350 millimeters, the tropical island country of Singapore still suffers from severe water shortage due to its land area of ??only more than 600 square kilometers. The per capita water resource is only 211 cubic meters, ranking second from the bottom in the world. Half of Singapore's 4 million residents rely on rainwater collected and stored for their daily water supply, while the other half relies on long-term water purchases from Malaysia under the Singapore-Malaysia water supply agreement. Under such circumstances, the protection and utilization of water resources has naturally become a national priority.