Aren't thumb drives 'waterproof' anyway? I mean, as long as it's dried out, no moving parts to seize or batteries to corrode.
I found a 128MB camera SD Card out in my back yard (it rains ~4 months/year) after I had tilled my yard up to replant, took it in and it fired right up, pics from 2000/2001 on it. Kind of the same principle between SD Cards and Thumb drives in different packaging...
I smell a way to charge more by claiming 'waterproof'. But, thankfully now I can take my waterproof USB drive down with my waterproof laptop so I can type my memoirs while SCUBA diving I guess... seriously, put your thumb drive in your pocket.
I'm never out in the rain long enough to worry about what's in my pockets, and if I'm going to be in the rain that long, I don't take electronics with me for gawd's sake!!
And finally in my rant, it doesn't look waterproof to me with that chinsy lip on it for the lid to snap over, more like water RESISTENT, which is hugely different... I think a real world test is in order...