Aquatic Ruin Zone

"Roaming Romans infest a beautiful forest and sunken lake. Explore an intricate maze. If you're underwater, breathe the air bubbles to keep from drowning. A countdown begins when your oxygen's running out."

- Sonic the Hedgehog 2 manual description

Aquatic Ruin Zone is the third Zone in Sonic the Hedgehog 2. As with most other stages in this game, Aquatic Ruin Zone consists of two standard Acts with a boss fight at the end of Act 2.

Description
A crumbling, semi-submerged stonework ruin, this Zone sports a couple of main terrain features that make it unique compared to the others. Water, for one; the movement speed underwater is much slower, so be prepared. Like with the rising chemicals from Chemical Plant Zone, if the player stays underwater for too long,  the player will eventually drown. To avoid drowning, stand near a small pile of air bubbles on the ground and wait for a big bubble to rise. There are also alternate paths to avoid the water altogether.

The ancient pillars that lie dotted around Aquatic Ruin are riddled with traps. Some will rise up when you approach and you must jump on them to destroy them. These can be dangerous in conjunction with the arrows fired out by other pillars, but otherwise they are not a threat.

Boss
The boss here has totem poles that rise up from the ground. Dr. Robotnik will then float above the poles and hit them in an alternating pattern with his hammer, causing the totems to fire an arrow. Once this arrow hits the other pole, you must jump on the arrow and hit the Egg Mobile.

Trivia

 * Several totem poles from the Aquatic Ruins (specifically during the boss battle) makes a cameo in Sonic Universe #53 during the Sonic the Hedgehog and Mega Man comic crossover event, Worlds Collide. It appears in the Skull Egg Zone while Sonic the Hedgehog, Mega Man, Miles "Tails" Prower, and Rush explore the zone to find the two remaining Roboticized Masters, which are Knuckles Man and Rose Woman.
 * In various preview magazines back in 1992, Aquatic Ruin Zone was named Neo Green Hill Zone (a name later used for the first level in Sonic Advance). This may have some connection to the concept that Sonic the Hedgehog 2 was, in its early planning stages, intended to have time travel like Sonic CD.
 * In the children's books published by Ladybird, such as Robotnik's Oil and Sonic the Hedgehog Adventure Gamebook 1, this zone was called Aquatic Ruins Zone instead of Aquatic Ruin Zone.
 * The boss for this stage can be very hard and frustrating when playing as Knuckles, as he cannot jump as high as Sonic or Tails.
 * The boss for this zone is often used in hacks for the unfinished Wood Zone.
 * In the Simon Wai prototype, the level music plays differently compared to the final.