Waterproof mascara is terrible for your lashes, it dries them out and makes them more brittle so that the breakage is worse, and because taking it off includes a lot of scrubbing it makes them fall out more often. If you already have thin, light, short lashes I seriously don't recommend it as it'll only make the problem worse and there are plenty of mascaras you can find that hold curl or clear mascara for the beach/pool when you want something in the water.
In reality, waterproof mascara doesn't work that well either. People forget that waterproof mascara still comes off in the pool because of the chemicals put in the water, in the ocean salt wears it away, and the minerals in lake water will also deteriorate the mascara. There are very few I've found that actually last longer than an hour between the water and oils in sunscreen.
Regular mascara, although still not great for the lashes, does a lot less damage, is easier to get off, and can look just as good if not better. If you hate going to the water without makeup on, I suggest a tinted moisturizer, a little concealer, a lip and cheek stain and a little clear mascara (which can also be used on the brows).