Question: We wanted to compare the safety and effectiveness of water-based exercise (but not swimming) training in people with chronic obstructive pulmonary disease (COPD) versus no exercise or a different kind of exercise in terms of exercise capacity and quality of life. Background: Land-based exercise training (such as walking or cycling) improves exercise capacity and quality of life in people with COPD. Water-based exercise training is an alternative mode of physical exercise training that may appeal to the older population, those who are unable to complete land-based exercise programmes and people with COPD who also have other physical and medical conditions. We did not include swimming interventions. Study characteristics: Five studies were identified up to August 2013. These studies included a total of 176 participants, with 71 people participating in water-based exercise training, 54 people participating in land-based exercise training and 51 people completing no exercise training. The average age of participants ranged from 57 to 73 years. The water-based exercise training programmes varied from four to 12 weeks in duration with attendance two to three times a week for between 35 and 90 minutes. The water-based exercises were designed to be as similar as possible to the exercises conducted in the land-based exercise sessions. The most common types of exercises were walking and cycling-type movements in the water, as well as strength training, most often using floats to increase the intensity. Key results: Participants who completed a water-based exercise training programme could walk an average of 371 metres farther than those who completed no exercise training and 313 metres farther than those who completed land-based exercise training. Quality of life also improved in participants who completed water-based exercise training, and significantly better quality of life was reported in these participants compared with those who completed no exercise training. Little information was provided to show whether these effects last for a long time after training has ceased. The effect that severity of COPD may have on benefits of water-based exercise training needs further examination. Two studies reported on adverse events; one minor adverse event was documented (from 20 people participating in water-based exercise training).