In the previous paper, a set of fundamental equations of motion for submersible were derived, and some experimental results were shown for verifying the equations. The present paper deals with further theoretical results for designing a submersible with idealized controllability proposed by authors, besides stability, response, and control forces According to the characteristics of motion, clarified with the graphed signal flow diagram, it results that the idealized controllability should include three conditions ; the center of gravity lies upon the symmetrical axis of the vehicle, forces of both gravity and buoyancy have the same quantity and are arrayed vertically to the longitudinal axis, and geometry of the vehicle is governed by some results. Thus the anothors conclude that this paper gives a theoretical basis for designing a submersible in view of the total control performance.