Questions about the cartesian diver

• What are the advantages of the Cartesian diver?

      A: You can sink and float with a Cartesian diver, while submarines alone, are buoyant.

• How come Cartesian divers are called Cartesian divers?
• What uses Cartesian divers?

      A: Well, sometimes divers use it, but submarines always use it.

• What is a Cartesian diver?

      A: Read this blog and find out!

• Why bother make a whole blog about Cartesian divers?