Islands of Komodo, Indonesia [huanqiu.com]

5. The islands of Komodo in Indonesia is best-known for its clear sea and multitudinous tropical marine life, which makes it become the Mecca of global divers. What more famous on Komodo is the largest lizard in the world -- Komodo Dragon.

The rising of sea level has already threatened the existence of the costal mangrove and beach. Meanwhile, the acidification and temperature changes of sea water might kill the coral around the islands.