Bordered by Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan, the 1,000-kilometre-long Caspian is the world's largest inland body of water. It is home to a range of native species -- from the seals to Caspian turtles and the famed beluga sturgeon -- and also to vast energy reserves, estimated at 50 billion barrels of oil. But pollution from the extraction of that oil and gas, along with declining water-levels due to climate change, has left many species under threat and the future of the sea itself at risk.