Abstract: The submersible drydock system of the present invention is one in which the buoyancy of the docking platform is altered to effect raising and lowering thereof. The submersible dock comprises a submersible platform having a buoyancy chamber formed therein. Foundations are located below the platform and a parallelogram linkage system interconnects the platform and the foundation. The parallelogram linkage system is operable to retain the platform in the generally horizontal plane in all positions during raising and lowering of the platform. A buoyancy control system is provided which communicates with the buoyancy chamber to vary the amount of air within the chamber to effect raising and lowering of the platform relative to the foundation.