An offshore structure comprises a base configured to be secured to the sea floor. In addition, the offshore structure comprises an elongate stem having a longitudinal axis, a first end distal the base and a second end pivotally coupled to the base. Further, the offshore structure comprises an upper module coupled to the first end of the stem. The upper module includes a variable ballast chamber. Still further, the offshore structure comprises a first ballast control conduit in fluid communication with the variable ballast chamber of the upper module. The first ballast control conduit is configured to supply a gas to the variable ballast chamber of the upper module and vent the gas from the variable ballast chamber of the upper module. Moreover, the offshore structure comprises a deck mounted to the upper module.