The Blue Whale Mobile Facility is a Siege Unit based off a blue whale, one of the world's largest mammals. Its chassis is so large that there are hallways and rooms located within the whale's chassis, which P.A.W. units may enter. While its faction is largely unknown, many believe it to be a secret B.A.R.K. mobile headquarters. However, even B.A.R.K. denies knowledge about the BWMF to fellow B.A.R.K. units and for the most part considers it an urban legend.

The BWMF has airjets that allow it to hover over land, but this ability has not seen use for as long as anyone can remember. For the most part, the whale typically spends its days hiding away in the Marina Trench where it is considered a separate dungeon. Like the Marina Trench, it is a Level 6 Dungeon.

Individual organs and arteries are also accessible by P.A.W. units. These organs and arteries are treated as rooms and hallways, respectively, and because they are still functioning, they are flooded with blood. The amount of blood that floods the areas varies depending on the whale's stress. Thus, it is very important to keep the BWMF calm while exploring its insides, as too much stress will cause rooms to flood entirely with blood at high pressure that can drown or crush P.A.W. units.