Background and AimsUnderwater endoscopic resection can be an alternative to standard resection techniques to remove difficult colorectal polyps. This video shows 4 cases of underwater resection of large colorectal polyps.MethodsUnderwater resection consists of complete filling of the lumen through the accessory channel, using an infusion pump followed by snare resection of the polyp. We present 4 cases: a 3-cm pseudodepressed laterally spreading tumor (LST) in the sigmoid colon, a 6-cm pedunculated polyp with a thick stalk in the sigmoid, a 7-cm sessile lesion in the midrectum, and a 4-cm LST in the distal rectum close to the dentate line, resected with a monofilament snare or a multifilament snare.ResultsAll tumors were successfully resected without any adverse events or residual lesions during follow-up.ConclusionsThe underwater technique is a good alternative to standard resection techniques to remove difficult colorectal lesions.