An electric-powered device includes (1) a skin-contactable surface and (2) a body having a water-resistant switch assembly. Preferably, the electric-powered device is useful in skin treatment and delivers mechanical forces on the skin. The switch assembly preferably includes, a substantially planar mount having an aperture, a rotatable shaft extending through the aperture, and a seal lining the aperture to restrict water movement along the shaft. In another aspect a water-resistant switch assembly includes first translatable element adapted for substantially planar motion in a first plane; a rotatable shaft, engageable with said first translatable element; a second translatable element adapted for substantially planar motion in a second plane, wherein said second translatable element is engageable with said rotatable shaft; a substantially planar mount having a through-hole and defining a third plane, wherein said rotatable shaft pierces said through hole and said third plane, wherein said third plane is substantially between said second plane and said third plane; and a seal surrounding said through-hole for rendering said through hole water-resistant.