A submersible inspection drone used for inspection can include a ballast system used to control depth of the submersible inspection drone. The submersible can be configured to communicate to a base station using a wireless transmitter and receiver. The ballast system can include a pressure vessel for storing fluid and a bag for inflating and deflating as it receives a fluid. Buoyancy of the submersible inspection drone can be provided by change in density of the pressure vessel as a compressible gas is expanded when the ballast bag is caused to inflate or deflate. A pump can be used to draw fluid from the ballast bag and store the fluid in the pressure vessel. In one form the pressure vessel can include a compressible fluid and an incompressible fluid, where the incompressible fluid is used to inflate and deflate the bag.