Aquatic Terrain Armored Transport The Aquatic Terrain Armored Transport , also known as the AT - AT swimmer , was a war vehicle used by the Galactic Empire , designed to be the aquatic equivalent of the land - based AT - AT walker . They were piloted by specially trained Imperial Army pilots . Characteristics . The AT - AT swimmer was manufactured in a joint venture between Kuat Drive Yards and Hydrospeare Corporation , and was derived from extreme modifications to the standard AT - AT that had been executed by the Imperial Army garrison on Kabaira . The command deck was attached to a broad area of the ship which contained passengers . It operated in deep sea operations alongside TIE fighter boat s and aquatic assault stormtrooper s and could be found in Imperial aquatic military bases . The AT - AT swimmer could also be deployed by the Y - 85 Titan dropship . It could carry 40 troops , and its cargo capacity was 600 kilograms . Its shell - like armor was designed to withstand and protect the vehicle from the crushing pressures of deep water , the effects of salt and water , and blaster fire . Its head was capable of providing firing arcs in all directions . The AT - AT swimmer had two modified heavy laser cannons , much like its land counterpart . Its main body was broader than that of the AT - AT to accommodate the four additional repulsorlift engines that keep it afloat . These four repulsorlift engines produced a powerful field strong enough to repel any object on the craft ' s ventral section , but it could be penetrated by strong swimmers where it was non - existent . By 137 ABY , the design was heavily modified . The version used by Darth Krayt ' s Galactic Empire could operate underwater and had shields . It included at least 6 laser cannons , including a rear double laser cannon to stem attacks from the rear , and was fitted with a launch bay containing at least five Shark underwater fighter s . The new design looked similar to the old one , although sleeker in design . The command bridge was also replaced by another similar to an AT - AT ' s command bridge . Additionally , these vehicles were known to have transported Sith Lords on several occasions . History . Galactic Civil War . The basis for the eventual Aquatic Terrain Armored Transport was created via the AT - AT Swimmer , which had been extreme modifications to the mech that were ordered by the Imperial Army garrison on Kabaira . This eventually ended up mass - produced , with some eventually being placed on Kaal , which proved enough of a problem to the Rebel ' s efforts on the planet that General Carlist Rieekan made a note while reviewing the official field manual for the Imperial Military , " " , that they will need to import attack subs from Mon Calamari . Action on Mon Calamari . At least one of the Sith Empire editions of these ships was employed during the Genocide of Mon Calamari on Dac in 137 ABY , where it was used to transport Darth Azard and Sith scientist Vul Isen to the Soheras Trench . Isen had created a Sea Leviathan there , and the two used the Force to awaken it and command it to slaughter the Mon Calamari prisoners of Imperial Extermination Camp 28 , and later search out and destroy every Mon Calamari in its path .