A civilian ship.
Civilian ships (民間船 Minkan-sen) appear in Episode 6 of Panzer Dragoon and Panzer Dragoon: Remake.
The Imperial Capital does not have roads, but it does have rivers as well as canals which serve a similar purpose. There are many of this type of ship that the people who live in the city use for transportation.[1]
Although the civilian ships can be destroyed, they do not count towards the shot-down ratio.[1]