The influence of topically applied tap water on the mechanical properties of human skin was studied in vivo by applying tap water to the ventral aspect of the forearms of 18 healthy volunteers for 10 or 20 minutes and then measuring distensibility, elastic retraction, and hysteresis. Significant increases in distensibility, resilient distensibility, and hysteresis were noted after 20 minutes of soaking. Most of these findings were already apparent after 10 minutes. This study shows that the epidermis plays a significant role in determining the mechanical properties of human skin. Possible practical implications of superficial skin hydration for plastic surgery such as tissue expansion and larger excisions are briefly discussed.