Background: Aquatic exercise has been shown to modify feelings of energy and fatigue in patients with chronic diseases. However, we are unaware of studies that have explored individual characteristics such as personality traits, sleep quality, and physical functioning that can determine whether or not a patient's mood improves with aquatic exercise. The purpose of this study was to identify individual characteristics associated with participants who reported a decline in feelings of energy or an increase in feelings of fatigue after a group aquatic exercise session. Methods: Participants were recruited from a community group aquatic program and asked to complete a series of surveys to assess their health status, sleep quality, and predisposition to feelings of energy and fatigue (trait energy and fatigue). Participants also completed a series of objective functional assessments. Current feelings of mental and physical energy and fatigue were measured on random days over multiple occasions before and after aquatic exercise. Participants were split into groups based on whether they reported an increase or decrease in feelings of energy and fatigue. Results: Participants (n = 11) completed a minimum of 2 sessions where mood was measured, and all 11 reported an increase in feelings of physical energy compared with the start of each session. All but one participant reported an improvement in feelings of mental energy. Interestingly, 4 participants reported an increase in feelings of physical fatigue, while 5 reported an increase in feelings of mental fatigue after exercise. All participants who reported an increase in feelings of physical fatigue also reported an increase in feelings of mental fatigue. When comparing the 2 groups, those who reported an increase in feelings of fatigue after exercise also reported low social functioning when compared with those who reported a decrease in feelings of fatigue. Discussion: Positive mood responses to exercise are associated with continued participation; therefore, this study provides insight into identifying individuals who consistently feel fatigued and may be less likely to complete an aquatic exercise program. These results suggest that either the modality or intensity of exercise may need to be changed for people with low social functioning as they may experience increased feelings of fatigue after a session of aquatic exercise. Future research with larger sample sizes is needed.