BACKGROUND: The occurrence of lower acute GI bleeding in the early perioperative period after colorectal anastomosis represents a life-threatening condition. The early treatment includes surgery or endoscopy, the latter being subject to complications associated with air insufflation and associated perforation. OBJECTIVE: To study the feasibility, efficacy, and safety of early perioperative water-immersion endoscopy to treat the source of bleeding in patients having undergone colorectal anastomosis. DESIGN: To prospectively study patients with active lower GI bleeding early after colorectal anastomosis and subject them to therapeutic water-immersion endoscopy instead of surgery. SETTING: University referral center for digestive surgery and endoscopy. PATIENTS: This study involved 2 patients presenting with active lower GI bleeding within 4 days after colorectal surgery. INTERVENTION: Instead of air insufflation during endoscopy, an underwater investigation was performed in each patient after colonic water immersion. MAIN OUTCOME MEASUREMENTS: Efficacy of therapeutic endoscopy. RESULTS: Water-immersion endoscopy in each case allowed us to identify the location of the anastomosis and the source of active bleeding. It allowed us to safely place clips on the active vessels and stop the bleeding. LIMITATIONS: Number of patients included, no comparison between conventional endoscopy and water-immersion endoscopy. CONCLUSION: Diagnostic as well as therapeutic water-immersion colonoscopy is safe in patients presenting with active lower GI bleeding in the early perioperative period after colorectal anastomosis.