Acute pulmonary edema may be induced by diving and strenuous swimming. We report the case of a diver using closed-circuit, scuba equipment who developed acute dyspnea, hemoptysis, and hypoxemia following a dive in 18 degreesC (64.4 degrees F) water and physical exertion during the swim back to shore. With the growing popularity of recreational scuba diving, emergency physicians are liable to be faced with increasing numbers of diving-related medical problems. Diving-induced pulmonary edema should be included in the differential diagnosis of acute hypoxemia, sometimes accompanied by acid-base abnormalities, when this is seen in a diver.