I floated the bed on my Taco once. Either I had a hell of a bow wave, or I just freakin' lucked out, because I had water coming over the hood with the stock intake, and it kept chugging along. It ran pretty rough for a few mintues afterwards, but I'm attributing that to the electronics getting wet. I think it's as waterproof as any other engine... if you keep the water out of it and the electronics, it'll be fine.