Abstract: The following specification discloses a combination backpack and gear bag for use by an underwater diver. The backpack is one wherein a container of gas such as a tank of pressurized gas is held on the back of a diver for purposes of providing a diver with breathing gas while diving. The backpack can be supported by straps across a user's body, or by means of a buoyancy compensator attached to the backpack for supporting the backpack and the tank therewith. The gear bag is such that it allows a backpack to be interconnected thereto. This is possible by means of insertion of the band or other connection means which holds the gas cylinder against the backpack through a passage in the gear bag followed by implacement of the gas cylinder within the gear bag and securing it with the connection means. The gear bag is oriented so that it can include within a portion thereof, carrying space for not only the cylinder, but other attendant apparatus, such as fins, snorkels, wetsuits, gloves, and other diving apparatus.