What this the difference between waterproof and water-resistant?
Waterproof mascaras are oil-soluble, which is why they are so good at repelling water. This is your best choice when you want the ultimate in staying power, nearly regardless of the activity.
Water-resistant formulas are water-soluble, which means, it can repel water as well, just not to the extreme as the waterproof variants. The one advantage to this type of formula is that it's much easier to remove.
Why is my mascara so difficult to remove?
The first question to ask is what type of mascara are you using? If it is a waterproof type, then use an oil-based cleanser. If it is water-resistant, then use a water-based cleanser, or simple soap and water will do as well. Oil & water do not mix, so using the correct tool for the task is essential.