Short answers, pulled from the story.
The Caspian is called a sea largely because of its size and its oceanic origins. Its southern basin is a remnant of the ancient Paratethys Sea, and its seafloor is oceanic basalt rather than continental rock. The legal question of whether it is a sea or a lake remained unresolved in international law until the 2018 Aktau Convention, which declared it legally neither.
The Caspian has a salinity of approximately 1.2 percent, about one third the salinity of average ocean water. This classifies it as a brackish body of water. Salinity varies significantly: the north is nearly fresh due to Volga River inflow, while the south, near Iran, is most saline because little riverine flow reaches it there.
The water level has fluctuated throughout history, falling from 1929 to 1977 and then rising until 1995. Since then smaller oscillations have continued. Climate projections now suggest the level could fall by as much as 21 meters by 2100 due to accelerating evaporation and desertification. In July 2025 the sea reached its lowest recorded level.
Caspian caviar comes from six native sturgeon species whose populations have been severely depleted by overfishing. Caviar specifically targets reproductive females, compounding the damage to the population. The high price, over US$880 per kilogram as of recent figures, means fishermen can afford to bribe regulators, making protective rules largely ineffective in many areas.
Five countries border the Caspian: Kazakhstan to the northeast, Russia to the northwest, Azerbaijan to the southwest, Iran to the south, and Turkmenistan to the southeast. Their coastlines collectively extend across a substantial stretch of the sea's perimeter.
Oil was extracted near the Caspian as early as the 10th century. By 1900, Baku had more than 3,000 oil wells. By 1941, the Baku region alone produced nearly 72 percent of the Soviet Union's total oil output. In 1994, the Contract of the Century opened the fields to international investment, and the Baku-Tbilisi-Ceyhan pipeline to Turkey opened in 2006.