Aquatic walking, which is influenced by the physical characteristics of water such as buoyancy, resistance, water pressure, and water temperature, is known to be effective for reducing stress on joints and increasing muscular strength. However, there is no consensus on its influence on blood pressure changes in elderly people. To address this uncertainty, we researched the effects of aquatic walking on the blood pressure of elderly people. Study participants were 48 females enrolled in a class to prevent the need for nursing care. In accordance with the diagnostic criteria for hypertension, participants were divided into two groups based on initial blood pressure measurements: a “high blood pressure group” with 27 people and a control group with 21 people. Both groups did the following program once a week for five weeks: 10 minute warmup, 15 minutes of aquatic walking (forward, backward, and sideways walking), 10 minute break, and additional 10 minutes of aquatic walking. Systolic blood pressure, diastolic blood pressure, heart rate, and average blood pressure of the participants were recorded. Results showed that the high blood pressure group showed significant decreases in systolic blood pressure after one week, and significant decreases in both diastolic blood pressure and average blood pressure from three weeks onward. No significant change was evident in the control group. However, comparing values measured immediately before and after aquatic walking showed that the control group had a significant post-aquatic walking increase in both systolic and diastolic blood pressures as well as a significant decrease in heart rate. Similar significant post-aquatic walking increases in systolic and diastolic blood pressures as well as a significant decrease in heart rate was also evident in the high blood pressure group from five weeks onward, once their measured values had improved. These results suggest that continuing an aquatic walking program will lower the blood pressure of elderly individuals meeting the diagnostic criteria for hypertension, but it is necessary to be attentive to physical condition because blood pressure increases immediately after aquatic walking in non-hypertensive individuals.