Aqua Shield

The Aqua Shield (アクアバリア), also known as Aqua (アクア), Bubble Shield or Water Shield, is one of the shield type power-ups that appear in the Sonic the Hedgehog series. It can be obtained by breaking Item Boxes with a water droplet symbol on them, which will then surround the playable character with a visible, but bouncy sphere-shaped shield, similar to a water bubble.

With an Aqua Shield, the playable character can take damage once without losing Rings or a life, and can move in underwater sections of the Zones without drowning. Also, when used by Sonic the Hedgehog in most cases, it allows the player to perform the Bounce Attack. In certain games though, the Aqua Shield can have different functions or have additional abilities.

The Aqua Shield was first introduced in Sonic the Hedgehog 3. While the Aqua Shield has not become as recurring power-up like the Lightning Shield, it has made some noteworthy appearances through the series.

Sonic the Hedgehog 3 and Sonic & Knuckles
The Water Shield made its first appearance in Sonic the Hedgehog 3 and its add-on continuation Sonic & Knuckles, alongside the Flame Shield and Lightning Shield, where it can be obtained by breaking monitors with water droplet symbols. The player can also collect Water Shields from Bonus Stages by getting blue gumballs with B-letter on them.

Like other shield type power-ups, when a playable character is equipped with a Water Shield, it will protect the player from one hit worth of damage from enemy attacks and/or contact, spikes, and other environmental hazards in the Zones by keeping the player from losing Rings or a life. After blocking a damaging blow however, the Aqua Shield will disappear, and the player is usually send flying slightly backwards. However, the Aqua Shield is not able to protect the player from falling into bottomless pits, being squeezed by Crushers, or the time limit of completing the stage running out, all of which give an instant death.

While equipped with a Water Shield, the player's playable character cannot drown from staying in underwater sections of the Zones for extended periods of time, meaning that the player can remain underwater for an unlimited amount of time without having to utilize any Air Bubbles to extend his/her time underwater.

When Sonic is using the Water Shield, it exclusively allows the player to use the Bounce Attack by pressing, or  right after doing a Spin Jump. When bouncing back into the air from the Bounce Jump, the player can do the Bounce Jump again by pressing, or  again.

Besides blocking damage and allowing the player to breath underwater, the Water Shield can also deflect regular projectile shots from Badniks, such as the Blastoids from Hydrocity Zone.

Sonic R
The Aqua Shield (called simply as Aqua in Japanese version) made another appearance in Sonic R, where it has drastically different functionalities.

Like other items in the game, the Aqua Shield can be picked up by the player from floating Item Panels with blue orbs on them during the race. After obtaining it, the playable characters get surrounded by blue shield, and the player is able to walk across the water surface on race tracks, whereas without the Aqua Shield, the player will sink into the water and move slower. After coming back to bare land, the player will then lose Aqua Shield instantly.

Sonic Advance 3
Although the Aqua Shield item box does not appear, it can be obtained through selecting Sonic and Cream together. When Sonic goes underwater he has it. It cannot be lost until he leaves the water; if an enemy hits Sonic, he will lose only his rings.

Sonic Generations
The Aqua Shield made another appearance in the console/PC version of Sonic Generations, where it is both an equipable Skill that grants the player an Aqua Shield once for each act, and an item box power-up for Classic Sonic. Here, the Aqua Shield retains all the effects it originally had in Sonic the Hedgehog 3 and Sonic & Knuckles.

The item boxes with the Aqua Shield appear exclusively in the Challenge Acts "Aqua Shield Challenge" and "With Your Powers Combined" where the player has to use its abilities to travers the acts. The Skill for the Aqua Shield can be bought from the Skill Shop for 300 skill points after clearing the "Aqua Shield Challenge" and cost 70 Skill points to be equipped. To activate the Skill in gameplay, the player has to press /.

Sonic the Hedgehog (1991)
The Aqua Shield appears in the 2013 re-release of the original Sonic the Hedgehog. To obtain it, the player must access the Level Select and in the "Items" category, they must switch to either "S1+S3" or "S2+S3". Some of the original Shield Monitors will then be replaced by the Aqua Shield. It also appears as one of the objects that can be placed freely in Debug Mode. Its functionality remains identical to that in Sonic the Hedgehog 3 & Knuckles.

Sonic Lost World
The Aqua Shield along with other elemental shields makes another appearance in Sonic Lost World, where it can be found in item boxes with blue bubble symbols on them. Along with other power-ups and items, the Water Shield is also an power-up that can be obtained from the Miiverse, where players can share power-ups and items with one another via Miiverse.

This does not grant the Bubble Bounce capability its original incarnation did, (due to this being mapped to the X/Y buttons when in midair anyway), but it does, as in its original incarnation, protect Sonic from drowning. In the Nintendo 3DS version, the Aqua Shield is a regular Item Box power-up in Tropical Coast.

Sonic the Hedgehog 2
The Aqua Shield appears in the 2013 re-release of Sonic the Hedgehog 2 where its purpose is near-identical to that in the 2013 re-release of the original Sonic the Hedgehog. To enable the Aqua Shield in gameplay, the player must first open the Game Config menu in the Level Select. In the Items category, the player must either highlight the second (the icon displaying the Shield with the three elemental shields) or fourth option (icon displaying Random with the three elemental shields) before starting a stage.

Trivia

 * Although the Water Shield appears in Sonic & Knuckles, there are no underwater sections in any of the zones presented in the game.
 * If the player is playing as Knuckles in Sonic & Knuckles, monitors with Aqua Shield have red water droplet marks instead of blue. This is due to Sonic and Knuckles sharing different color palettes in the game.