I've always lined my lower waterline for as long as I've been wearing makeup. For the longest time, all I would do would be to rim my lower waterline with black eyeliner and be done with things.
These days, I tight line my top waterline and wearing a gold/nude color eyeliner on my lower waterline (unless going for a more dramatic look) and I love it! My eyes still pop thanks to the top, and they look wide & bright thanks to the bottom!
Basically, she's breaking down all the different ways you can use your waterlines to change your look!
Look 1: Light on top & bottom - widens eyes at both top AND bottom, but can seem too "open" on some
Look 2: black on top, light on bottom - adds definition to the top of the eye & to top lashes
Look 3: black on both - eyes look smaller, but POP much more!
Look 4: No makeup for comparison!
So, use your waterline (carefully!!)
Lining here can cause serious irritation for some people, so be careful! But if you want to look more awake or cancel out eye redness, use light pencils on either bottom or both waterlines. If you want a dramatic look, go for black tightlines & waterlines!