U-Boat Watch Darkmoon 40 Brown Black Curve Vintage 9547. The Darkmoon watches feature an electromechanical movement completely immersed in an oil bath, with a compensating bubble, which provides an amplified view of the dial for the wearer as if there were no glass. U-BOAT launches this new range of watches with a new curved dial, under the domed sapphire glass, further emphasizing the 3D effect.