The Aqua Shield Challenge is the third Challenge Act of Chemical Plant Act 1 in the console/PC version of Sonic Generations. It is unlocked after clearing every Stage in the classic era and is playable only as Classic Sonic.
This Challenge Act takes place in the Chemical Plant Act 1, where the player controls Classic Sonic. The player is given many constantly-regenerating Monitors which are scattered all throughout the stage, everyone on of the containing an Aqua Shield. As such, the Challenge Act requires the player to take advantage of the shield's Bound Jump in order to properly make it to the Goal Ring. Upon completion, this Challenge Act makes the Aqua Shield skill available for Classic Sonic in the Skill Shop.