The present invention is directed to an offshore access system that includes a support frame designed to be supported by grating positioned above horizontal structural members of the offshore structure. A support sleeve is attached to the support frame. Within the support sleeve there is included a vertically slidable and rotatable post. A mobile works platform is attached to a lower end of the vertically slidable and rotatable post. The work platform has a U-shaped configuration in one embodiment to provide maximum access to vertical structural members.