Harvester Submersibles are propeller equipped Imperial vessels, that operate under water to harvest deep-growing seaweeds. In a sense, they are the aquatic versions of a Mega-Harvester used for underwater aquaculture. They only appear in the Urdesh: The Serpent and the Saint novel.
- Length: 20-24m; approx
- Mass: 500-640 tonnes; approx
- Crew: 3 crew
- Acceleration: 15 knots; approx
Harvester Submersibles use their bows' slashing swathers to collect the seaweed, which Flatboats are unable to reach, and are strong enough to bulldoze their way through entire forests of the plants. It takes at least three crew members to operate the Harvester, which includes a pilot, co-pilot and an engineer to maintain the vessel's Promethium engine.
However, the engine is so loud, that it can be heard a world's surface and its crew must be near each other in order to be heard. The vessel is also equipped with two Saviour Pods, in case its crew needed to escape, and they are located on its waist's port and starboard sides. The Harvester Submersible is now considered an old Submersible model type and was ancient even during the Sabbat Worlds Crusade. As the Crusade raged on Urdesh, a Harvester Submersible was converted for war against the Blood Pact and Sons of Sek who invaded the world. It was equipped with bolted-on armour, jerry-built redundant systems and its swathers were replaced with whatever spare weapons that could be lashed onto it.