Waterline eyeliner

This is one item we can’t always test, especially when purchasing online. What ingredients should I be looking for if I’m wanting to line my waterline?

Looking at Amazon, “kohl” can mean anything and is often attached to “waterproof “, so I’m not asking about keywords or product recommendations (we’re all in different countries too). If anyone knows, can you please shed light on the science of it, what to look for, what to avoid!