Purpose <p>Human vision becomes blurred when seeing objects or stimulus through the water medium, called as water-induced blur (WIB). This study investigated the effects of simulated WIB (SWIB) on high-contrast visual acuity (HCVA), low-contrast visual acuity (LCVA), and Vernier acuity among swimmers and non-swimmers.</p> Methods <p>The performances of 20 swimmers and 20 non-swimmers were compared under both baseline and SWIB conditions. The WIB was simulated using a system that splashed water against a transparent glass tank through which the stimuli were viewed on a monitor. HCVA, LCVA, and Vernier acuity were assessed using the Freiburg Visual Acuity and Contrast Test (FrACT₁₀).</p> Results <p>The baseline HCVA and LCVA (in logMAR) were similar (<i>p</i> ≥ 0.05) between swimmers (HCVA: − 0.11 ± 0.05; LCVA: 0.05 ± 0.03) and non-swimmers (HCVA: − 0.09 ± 0.04; LCVA: 0.05 ± 0.03). While both groups experienced significant visual decline with SWIB, swimmers demonstrated superior performance compared to non-swimmers. Specifically, non-swimmers showed greater deterioration in LCVA (0.58 ± 0.13) compared to swimmers (0.43 ± 0.08). Similarly, the mean baseline Vernier acuity (in arcsec) was comparable between swimmers (13.69 ± 5.25) and non-swimmers (14.05 ± 3.37). Whereas with SWIB, Vernier acuity deteriorated more among non-swimmers (64.01 ± 14.42) than swimmers (49.14 ± 20.14).</p> Conclusion <p>The results revealed significant impairments in HCVA, LCVA and Vernier acuity with SWIB for both swimmers and non-swimmers. However, swimmers consistently demonstrated superior performance (LCVA and vernier acuity) compared to non-swimmers, suggesting regular exposure to WIB may induce adaptive changes in visual processing.</p>