An internal unit is incorporated in a body of a submarine apparatus. The
internal unit comprises a plurality of system units placed in a
predetermined arrangement, and coupling bars fixed to coupling-bar fixing
surfaces of the system units by screws so as to couple the system units in
the predetermined arrangement. The system units include at least one
electronic-circuit printed board having a part to be adjusted. The
coupling-bar fixing surfaces are located at positions shifted from the
electronic-circuit-printed board.
