The purpose of this study was to use surface electromyography to measure the muscular activity during the sit-to-stand task in water and compare it at three different chair heights. Ten healthy young adults [5 males and 5 females (mean ± SD): age, 22.0 ± 3.1 yr; height, 172.8 ± 9.0 cm; body mass, 63.9 ± 17.2 kg] were recruited for study. We used a telemetry EMG system on the following muscles on the right side of the body: quadriceps (vastus medialis and rectus femoris), long head of the biceps femoris, tibialis anterior, gastrocnemius medialis, soleus, rectus abdominis, and erector spinae). Each participant performed the sit-to-stand test five times at each of three different chair heights underwater. No significant differences in muscular activity of all muscles measured during the performance of the sit-to-stand exercise in water were found for any of the chair heights. This study for the first time described the neuromuscular responses in healthy subjects during the performance of the sitto-stand task in water at different chair heights. The muscular activity of lower limb and trunk should be considered when using the sit-to-stand movement in aquatic rehabilitation.