Explanation

The Caspian Sea is completely enclosed.

Note:

(Completely enclosed Means) It's a large, saline lake surrounded by land, with no natural outlets to any other ocean or sea

Additional information 

The Caspian Sea is the world's largest inland body of water

 It lies between Europe and Asia

It covers a surface area of 371,000 km2

Five countries border it:

1. Kazakhstan to the northeast
2. Russia to the northwest
3. Azerbaijan to the southwest
4. Iran to the south
5. Turkmenistan to the southeast. 

The name of the Caspian Sea is derived from the ancient Iranian Caspi people.