Mustelids like ferrets, minks, and otters, provide an exciting opportunity to study locomotor transitions, particularly the evolution of aquatic adaptations. This clade spans a broad range of aquatic dependence, from primarily terrestrial species to highly aquatic otters. Water is a denser and more viscous medium than air; animals swimming with drag-based paddling must generate propulsion by pushing against a resistant medium. This typically results in slower, but more forceful limb strokes compared to terrestrial stride cycles. Osteological studies seem to support this, linking an increased robustness of the long bones of the legs to aquatic specialisation. In this study, we hypothesise an increase in force-generating potential for muscles linked to either propulsion during the swimming power stroke or the recovery stroke, and longer fascicle lengths for muscles contributing to increasing the stroke amplitude. To test these hypotheses, we performed detailed manual dissections of the forelimbs across five mustelid species that represent different levels of aquatic specialisation. We quantified the muscle architecture, including physiological cross-sectional area and fascicle length, which serve as proxies for force-generating potential, and excursion potential, respectively. Results suggest that general patterns are in line with our hypotheses. Ongoing analyses of the data will help to pinpoint the specific muscles that contribute most to these patterns of variation.