One of my customers had a BikeRay IV literally fill up with water and fail during use in the rain, which is why my lights (DesignShine) got "waterboarded" over on MTBR (link posted earlier). If it were me, I'd want to know that my lights were waterproof and not merely water-resistant. The power cord entry on the MS lights is definitely far short of waterproof. Corrosion over time can become an issue. So, although I'd agree, the majority of the time, water won't be an issue, there are always those exceptions to the "rule."