they don't encourage running water through it, but it just might protect your device in a rainstorm or sudden dunking from a canoe / kayak or loss of footing in a river crossing.
In all fairness, everything is only "water resistant". I thought I read somewhere that "waterproof" should only be applied to products that can repel water/keep a dry environment for at least 1 hour at some atmosphere completely submerged.
If they cannot guarantee a time period, then it is "water resistant". In my opinion at least.