Water exchange method has been shown to reduce medication requirement and pain experienced during colonoscopy. It may increase the adenoma detection rate (ADR). Water exchange provides salvage cleansing and the refractive index of water (n equals about 1.3) is larger than that of air, which creates optical distortion that likely contributes to objects appearing larger underwater, making smaller lesions easier to visualize and it may help draw attention to those smaller lesions during withdraw. These principles facilitate to the higher adenoma detection rate.