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I don't find this to make my mascaras perfectly waterproof, like your traditional waterproof mascara, but it sure does give that little extra layer of protection from water. It doesn't make your mascara difficult to remove like many waterproof mascaras can do. It also doesn't make the lashes feel hard or crunchy. And I actually notice that it helps keep flaky mascaras on better. I usually don't have problems with smudge-y mascara, so I can't vouch for that, but given the fact that it reduces flakes from certain mascaras, I would assume it would at least somewhat help with smudge-y mascaras.
The test I did on this mascara was to take my wet fingers and press down on the lashes. The first few presses didn't allow anything to transfer or come off, but after a few seconds messing with the lashes, the mascara did start to come off. So although it didn't make them completely waterproof, it added a little bit of extra something to make the mascara withstand more water than usual.
I don't think I would trust this product if I were going to be swimming (or crying for that matter), but perhaps on a rainy day, it would survive.
Overall I would recommend this if you're just looking to experiment with your mascaras. I find it has that extra little something that makes your mascaras just a little better than before. And for $3 ($1.50 on sale), it's not a bad price or product.
Thanks for reading!