It is water-resistant, but definitely not waterproof. The packaging notes that you can wash it off with warm water, and in my experience this is true.
Also, it is the most wonderful mascara I have ever tried! Love that stuff.
Fairy Drops is a water- and sweat-resistant, volumizing mascara with a brush so unique it is patented in Japan. It calles itself not waterproof, but water-resistent so it should hold up well against water, but it doesn't claim to be completely waterproof.
I hope this helps you.