Mental Health Indicators in Older Men Practising Aquatic Exercise and Multicomponent Exercise: An Exploratory Cross-Sectional Study

Background/Objectives: Regular physical exercise is considered a relevant strategy for promoting physical and mental health in older adults. However, studies using exclusively male samples that directly compare different exercise modalities in mental health indicators remain scarce. Therefore, this study aimed to compare mental health indicators between older men practising aquatic physical exercise and older men practising multicomponent physical exercise. Methods: This exploratory cross-sectional study included 17 older men, divided into two groups: aquatic exercise (AE; n = 8; 70.8 ± 4.5 years) and multicomponent exercise (ME; n = 9; 75.4 ± 4.1 years). We assessed the following mental health indicators: self-esteem (Rosenberg Self-Esteem Scale); life satisfaction (Satisfaction with Life Scale); depressive symptoms (Geriatric Depression Scale); and perceived stress (Perceived Stress Scale). As sample characterisation variables, body composition parameters were analysed: body weight, bioelectrical impedance-derived visceral fat level, percentage of fat mass, and percentage of muscle mass. Results: In the unadjusted parametric analysis, life satisfaction differed significantly between groups, with higher values in the ME group (p = 0.029; d = −1.174; 95% CI: −2.20 to −0.12). However, this difference no longer reached the threshold for statistical significance after the Bonferroni correction for multiple comparisons (adjusted p = 0.116) or in the non-parametric sensitivity analysis (p = 0.054). We observed no statistically significant between-group differences in self-esteem, depressive symptoms, or perceived stress. Conclusions: In this sample of older men, the unadjusted parametric analysis showed a between-group difference in life satisfaction, with higher values in the multicomponent exercise group. However, this finding did not remain statistically significant after correction for multiple comparisons or in the non-parametric sensitivity analysis. No statistically significant between-group differences were detected in the remaining mental health indicators analysed. Nevertheless, given the small sample size and limited statistical power, the absence of statistically significant differences in these indicators should not be interpreted as evidence of similarity between the exercise modalities. These findings should be considered exploratory and interpreted with caution, also taking into account the cross-sectional design of the study.