Background: Postural stability enables humans to maintain the center of mass of their body within their base of support. Nevertheless, over time, such stability is affected by different factors such as age, repetitive strain, and accidents. Although studies in this field have investigated the effectiveness of hydrotherapy, only a few of them have explored its influence on postural stability, which is reflected in a lack of research that estimates its impact on rehabilitation. Aim: To determine the immediate and final effects of an aquatic routine protocol on the postural stability of elderly subjects. Methods: The postural stability of 20 adults over 60 years of age was analyzed using electromyographic and baropodometric methods. Electromyographic signals were obtained from the tibialis anterior, soleus, both gastrocnemius, vastus medialis, and biceps femoris to calculate the coactivation percentage of the muscles in charge of postural stability. The baropodometric data were collected to analyze the area of the stabilometric ellipse, mean plantar pressure, and weight distribution percentage. Results: The outcome of both methods revealed improvements in the elderly patients after the aquatic routine protocol was applied, which indicates that the type of water exercises implemented in this study has positive effects on their postural stability. Conclusion: The postural stability of the elderly participants was improved after each session because their stability index decreased along with the electrical activity of some muscle pairs, their body weight was better distributed, and the area of body oscillation was reduced. However, this effect was immediate and not final.