Objective: The aim of this study was to investigate the adaptations of a water-based training program as well as the detraining and retraining effects on physiological parameters in patients with coronary artery disease (CAD). Methods: Twenty-one patients were separated in an exercise group (n = 11) and a control group (n = 10). The exercise group followed three periods: training, detraining and retraining. Each period lasted 4 months. During the training and the retraining periods, the patients performed four sessions of water exercise (not swimming) per week. Results: The water-based program was well-accepted and no adverse effects were observed. The exercise group improved (p < 0.05) their stress-test time (+11.8%), VO<sub>2 peak</sub> (+8.4%) and total body strength (+12.2%) after the training period; detraining tended to reverse these positive adaptations. Resumption of training increased the beneficial effects obtained after the initial training period (exercise stress: +4.5%; VO<sub>2 peak</sub>: +6.6%; total strength: +7.0%). The patients in the control group did not show any significant alterations throughout the study. Conclusion: Water-based exercise is safe and induces positive physiological and muscular adaptations in low-risk patients with CAD. These could be reversed, however, after the cessation of exercise. This is why uninterrupted exercise throughout life is a must.