Watertight luminary for fluorescent lamps (1) with incorporated catoptrical, or diffusive reflector (2) for light direction for the increase of its luminary efficiency. The metallic base (3) of the electrical components of the watertight luminary (1) is fixed at the bottom of the plastic base (4) so that it has smaller dimensions and, consequently, less material and lower assembling time comparing to the metallic base which would be fixed as a cover (8) in the open upper side of the plastic base. With the support of the metallic base (3) at the bottom of the plastic base (4) of the luminary, there is ample space in the upper open side of the plastic base (4) that allows the placement of the reflector (2) at the optimal distance from the fluorescent lamps (5) so that the desirable concentration and direction of light can be achieved. The reflector (2) for the light direction is shaped from plastic film of at least one reflective surface in an integrate form. The reduction of construction cost of the reflector (2) and of the metallic base (3) of electrical components in combination with the appropriate distance of the reflector (2) from the fluorescent lamps (5), allows the standard and permanent incorporation of the reflector (2) for light direction in the watertight fluorescent luminary (1) and results in the increase of its luminary efficiency by 15%.