Imperial submarine

In 18 BBY, after the Battle of Dac City on Mon Cala, the Galactic Empire utilized at least one submarine to rescue Darth Vader from the depths of the Great Ungeness Trench.

Behind the scenes
The submarine debuted, albeit unnamed, in Darth Vader: Dark Lord of the Sith 15: Burning Seas, Part III, a canon comic written by Charles Soule, pencilled by Giuseppe Camuncoli, and released in 2018.

Appearances

 * Darth Vader: Dark Lord of the Sith 15: Burning Seas, Part III