U-Boat Watch Darkmoon Black SS 8463. The U-Boat watches Darkmoon goes beyond the boundaries of traditional design, combining innovative features with retro style lines. The Swiss electromechanical movement is completely immersed in a low viscosity lubricating oil. The oily liquid flows into the dial making it an absolute and deep black and creates an ever moving compensation bubble that surprisingly amplifies view of the hands that seem to flow free as in the absence of the glass.