A buoyancy pump device for use in fluid. The buoyancy pump device includes a buoyancy block housing defining a buoyancy chamber therein through which the fluid may flow. A buoyancy block is disposed within the buoyancy chamber to move axially therein in a first direction responsive to rising of the fluid in the buoyancy chamber and a second direction responsive to lowering of the fluid in the buoyancy chamber. A piston cylinder is connected to the buoyancy block housing and has at least one valve disposed therein operating as an inlet in response to movement of the buoyancy block in the second direction and an outlet in response to movement of the buoyancy block in the first direction. A piston is slideably disposed within the piston cylinder and connected to the buoyancy block, the piston being moveable in the first and second directions and responsive to movement of the buoyancy block in the second direction to draw a gas or liquid substance into the piston cylinder through the at least one valve, and responsive to movement of the buoyancy block in the first direction to output the gas or liquid substance through the at least one valve.