The waterline is that inside-line of your eyelids where a lot of women like to apply makeup. Tightlining or waterlining is the technique used for drawing eyeliner inside, tight against the lashes of the upper lid or lower eyelid margin, which make the eyelashes look longer.
Who doesn't love getting glammed up with false eyelashes. When applying falsies, technique and safety are paramount. The makeup trend-du-jour is to apply/glue fake eyelashes underneath the lash line, on the waterline. And we're here to put the kibosh on that method.