Aquatic assault stormtroopers, also called seatroopers or aquatic troopers, represented a distinct specialization within the Imperial stormtrooper ranks. The Galactic Empire deployed them to assert their authority across the numerous water-dominated worlds under their dominion. Whether they were connected to the aquatic Imperial navy remains a mystery.
The Imperial military adapted much of its standard gear for underwater operations, creating specialized aquatic garrisons, uniquely designed TIE fighter boats, and formidable AT-AT swimmers. The seatrooper's armor drew inspiration from the lightweight scout trooper model. It was layered over a specialized two-part environmental suit, providing protection from extreme temperatures and toxic aquatic environments. Furthermore, the scout trooper helmet underwent modifications to integrate oxygen tubes and filter out hazardous chemicals, enhancing the aquatic sea trooper corps' adaptability. The seatrooper's armor, engineered for operations on planets like Dac and Tibrin, was pressure-sealed to withstand up to ten atmospheres and incorporated a rebreather, enabling underwater stays exceeding one hour. This armor offered greater flexibility compared to standard stormtrooper gear, preserving and even improving a trooper's underwater agility. A back-mounted propulsion unit, along with propulsion boots featuring snap-down flippers, augmented a soldier's swimming capabilities. Given the detrimental effects of water on blaster range, seatroopers typically carried a blaster rifle/speargun hybrid as their primary weapon. In 137 ABY, the seatroopers serving Darth Krayt's Galactic Empire utilized plasma rifles.
The standard seatrooper utility belt contained items such as high-tension wire, grappling hooks, spare blaster power packs, ion flares, concentrated rations, a backup comlink, medpacs, replacement rebreather filters, and a compressed air inflatable shelter.
Additionally, seatroopers employed the SG-4 blaster rifle, which could fire small harpoons underwater.
Aquatic assault stormtroopers were the evolutionary successors to the clone SCUBA troopers who fought in the Clone Wars as part of the Grand Army of the Republic.
A variant was observed on Iskalon sometime after 3 ABY. This version consisted of a standard stormtrooper helmet and upper body armor worn over heavy white coveralls. The back-mounted propulsion unit included an air supply, but the propulsion boots lacked flippers. The Empire deployed thousands of aquatic stormtroopers in the conquest of Manaan.
Seatroopers, alongside representatives from every specialized Stormtrooper Corps, were assigned to Darth Vader's personal Death Squadron. Following the Battle of Endor, largely due to the seatroopers' aquatic combat skills, the Rebel Alliance enlisted the Mon Calamari Knights to assist in liberating various aquatic worlds, as they were uniquely equipped to counter the seatroopers.
During the Second Imperial Civil War, the Imperial Army also deployed Aquatic assault stormtroopers on Dac for the extermination of the Mon Calamari population, under the orders of Emperor Darth Krayt. After the One Sith were overthrown, control of the seatroopers passed to the Galactic Federation Triumvirate, a new galactic government formed by the Fel Empire, the Galactic Alliance Remnant, and the New Jedi Order. Seatroopers under the command of Imperial Knight Yalta Val participated in the liberation of Mon Calamari and Quarren slaves, who had been forced to construct ships for a pirate organization led by the renegade Sith Darth Luft. The seatroopers were instrumental in capturing the pirates, who were then turned over to the authorities.
The initial appearance of seatroopers was in the Marvel Comics story Star Wars (1977) 74, released on May 17, 1983. Subsequently, seatroopers featured in several Legends Expanded Universe works, including the Imperial Sourcebook, Death Star Technical Companion, and the Dark Horse Comics series Star Wars: Legacy and Star Wars: Legacy Volume 2.