Introduction: aquatic exercises have been increasingly suggested to the population. Despite evidence on the benefits of high-intensity interval training in aquatic environments, scientific production still needs to be improved. Research involving middle-aged and older individuals usually seeks physiological responses from the assumption that they are sedentary. Objective: to assess the physical fitness, lipid profile, and glycemic control of active middle-aged and older adults undergoing aquatic high-intensity interval training associated or not with intense water walking. Methods: it is a quasi-randomized clinical trial composed of 45 active middle-aged and older adults subdivided into two groups with aquatic high-intensity interval training in the absence (AHIIT) or presence (AHIITW) of intense water walking. Participants were dosed with biochemical parameters, bioimpedance analysis, and physical and cardiopulmonary tests at the intervention’s beginning and end. Results: both groups showed increased HDL, reduced LDL, and hemoglobin glycated, with increased endurance and strength of upper and lower limbs. The AHIIT group showed a lean mass gain and fat mass decline compared to the AHIITW. The intense walking promoted an increase in oxygen ventilatory equivalent, maximum oxygen consumption, and the task metabolic equivalent at values like the AHIIT. Conclusion: our findings indicate that high-intensity aquatic training holds the potential to enhance the lipid profile of individuals. However, the incorporation of pool walking into the training regimen did not lead to any notable differences in this regard. Conversely, the inclusion of pool aquatic exercises did result in improved functional capacity among participants. Brazilian Registry of Clinical Trials (ReBEC): #RBR-99b6jr6