Hydrocity Zone

Hydrocity Zone is the second zone in Sonic the Hedgehog 3 (or Sonic 3 & Knuckles). This is the most water-filled level in the game, and several parts of the level takes place underwater. This is also the only level in the game to feature the air bubbles (except the bubbles inside the balloons in Carnival Night Zone), which prevents the character from drowning. However, if you find a water shield you don´t need the air bubbles.

Trivia

 * In the first act, statues resembling Sonic can be seen at the top of the background.