AQ-series battle droid

With a height of 2.83 meters and classification as a droid tank, the AQ-series battle droid, a creation of both the Haor Chall Engineering Corporation and the Techno Union, displayed a more robust build compared to the standard B1 model. It featured a substantial chest with ridged shoulders, extended legs, and a polygon-shaped head that could retract into the droid's body to minimize drag during aquatic maneuvers. Its feet were designed to adapt, functioning as standard walking supports on land or transforming into propellers for underwater propulsion. The droids were also painted blue to blend in with their aquatic environments.

Specifically engineered for amphibious operations, the aqua droid was the Techno Union's adaptation of the B2-series super battle droid for underwater combat. These aqua droids exhibited greater agility and a more streamlined form underwater than their B2 counterparts on land. Nevertheless, their programming ensured they remained just as dangerous and aggressive. Despite their remarkable underwater mobility, these droids moved with a slow, cumbersome gait on land, similar to super battle droids, making them vulnerable to enemy snipers. For defense, each aqua droid was armed with a single retractable laser cannon on its right wrist and could also use its strong arms to inflict significant damage on enemy vehicles, such as Kamino submarines, underwater.

The droid army of the Confederacy of Independent Systems utilized aqua droids during the Clone Wars. They were observed during their attempted invasion of Kamino, a water-covered planet, in 21 BBY. Several units were secretly deployed to the planet under the command of Supreme Commander Asajj Ventress. When a Confederate Fleet commanded by General Grievous entered orbit and engaged the Republic's defense fleet, debris from the Separatist support vessels rained down into the ocean. The Republic dismissed this debris, unaware that it concealed assault ships that Ventress's aqua droids began assembling. Jedi General Obi-Wan Kenobi, suspicious of Grievous's willingness to sacrifice his support ships, discovered the droids' activities. He investigated underwater in a submarine. Upon finding Ventress's aqua droids, his craft was quickly surrounded as the droids attached themselves to the submarine and began disabling its engine systems. In a desperate move, Kenobi abandoned his craft and escaped the aqua droids by riding a nearby aiwha.

Almost immediately after their discovery, the aqua droids initiated their attack on the Kaminoan cloning facilities in Tipoca City, deploying assault craft that breached the hull of the facilities at various points and released aqua droids and B1-series battle droids into the facility. Despite their rapid spread throughout Tipoca City, they were soon pushed back by local clone forces led by their Jedi Generals. The primary objective of the droid assault was to divert attention, enabling Ventress to seize the genetic template of Jango Fett and halt the Republic's clone production. However, this plan was foiled by Jedi General Anakin Skywalker, forcing Ventress and the remaining Separatist forces to withdraw. Although unsuccessful in their objectives, the attack on Kamino boosted Separatist morale, demonstrating the vulnerability of all Republic worlds.

Later in 20 BBY, Riff Tamson effectively deployed aqua droids during the civil war instigated by the Separatists on Mon Cala. Following Tamson's murder of Lee-Char's father, his aqua droid army was unleashed after the Quarrens switched their allegiance from the Republic to the Separatists. Tamson led his combined force of aqua droids and Quarrens against the Mon Calamari, Padmé Amidala, and Anakin Skywalker, thus starting the conflict. Shortly after, a company of clone troopers under Commander Monnk, along with Jedi Master Kit Fisto and Skywalker's Padawan Ahsoka Tano, arrived to reinforce the Republic, compelling Tamson, the Quarren, and the aqua droids to retreat. Tamson and his droids regrouped and received reinforcements in the Separatists' second wave, spearheaded by the cyborg hydroid medusas. Together, they forced Captain Ackbar, the Prince, and their Jedi escort to seek refuge in the caves.

After Tamson gave the order to destroy the Jedi's cruiser, multiple aqua droids ambushed the Jedi and the Prince amidst the falling debris. Soon after Skywalker's group destroyed the building housing the sonar and tracking devices, Tamson ordered his forces to prepare for an assault. An aqua droid informed Tamson of two Jedi groups: one in the lower city center and another freeing prisoners near the coral base. In response, Tamson dispatched reinforcements from Count Dooku to these areas, resulting in the capture of all the Gungans, Amidala, Skywalker, Fisto, and most of the Mon Calamari, except for Lee-Char.

Many aqua droids were assigned as guards in the prisoner camps, while others conducted extensive searches, forcing Lee-Char and Tano to remain in hiding. A group of Mon Calamari prisoners were escorted into one camp by several aqua droids, while Tano and the Prince infiltrated the same camp. Shortly after, an aqua droid spotted them conversing with Ackbar and other Mon Calamari. The droids surrounded them, but Lee-Char demanded to speak with their commanders, a request that was granted. Later, aqua droids escorted the prisoners to Lee-Char's execution, intending for them to witness his demise. However, the Prince and Tano's plan succeeded, leading the Quarren to defect and assist their Mon Calamari allies. With the combined efforts of the Jedi, clones, and Gungans, most of Tamson's forces, including the aqua droids, were defeated.