A waterproof vehicle or equipment cover with passive barometric air-pump is disclosed and is characterized as having a flexible, fluid impervious first layer of material, a flexible, porous second layer of material sized to generally correspond to the first layer of material and attached thereto at the perimeter of the second layer to create an enclosed void defined by the first layer and the second layer, and a plurality of flexible tubes, each tube having a first open end and a second open end, and having a plurality of apertures defined thereby, wherein each tube is located in the void, in spaced apart relation, to thereby permit ingress of gaseous fluid from the first end of each tube to the void and egress of gaseous fluid from the void to the second end of each tube. When the cover is placed over the vehicle or equipment with the first layer exposed to ambient conditions and the second layer proximate to the vehicle or equipment, the cover will shelter the vehicle or equipment from ambient conditions and the perforated, open-ended tubes will utilize ambient pressure differentials to create a passive circulation of air into and out of the enclosed void and other isolated areas between the outer layer and the covered vehicle or equipment.