Underground water level of the planet ZEBES. Draygon is the boss here.
The Maridia is fun to go into without the gravity suit. =/
The underground ocean of Planet Ceres, of the Metroid Series. Typically accessed through the n00b tube or from the Wrecked Ship. Frequently considered to have the best atmosphere of any area in Super Metroid.
Have you heard that creepy music in Maridia?