The mini-sub had armor protection for the droid pilot, as well as a single, large laser cannon. They were transported to underwater battlefields inside specialized carriers.
Many of these underwater craft were ripped to shreds by the riding beasts of the Mon Calamari Knights.
The Xi Char provided underwater conversion kits for the MVR-3 speeder bike to the Trade Federation as compensation for the Xi Char failing to figure out how to make the manta droid subfighter transform like the Vulture-class droid starfighter.
- "Ask the Master" — Star Wars Insider 81
- The New Essential Guide to Droids