I'd doubt the light is waterproof, if we're talking about the bastid light.
I may not have a true impression of the reliability of this light as I only seem to see the threads relating to a failure.
However, it does seem that reliability is a bit hit-n-miss.
I've seen issues highlighted related to the electronics inside the light, batteries failing, chargers failing and who can tell how they'll be standing up in a year or two, with regular use throughout the night riding season.
I realise that there are those on here who love the Bastid Light, but if your budget can stretch to it, then I'd buy from one of the more established brands.
Stuff like Hope and Lupine might only be able to match my light on quality, if they're lucky (and I've yet to be convinced), but they are made and priced to make a significant profit.
good luck in finding your light.
L.