The dirt roads out my way flood every spring. But they get washed out and slick as well. Anything on less than a 38'' Super Swamper is NOT going to make it through that, if the water reaches bumper height. When the water gets that high, I turn around. We've been stuck many time right around that height. And with the new truck, I don't want water in the cabin anyways.
So a snorkle is useless to me. As for dust. 4 air filters cost nothing, and fit under the seat. So make sure you actually can make use of one, otherwise you end up looking like another expo poseur. Which is becoming quite popular. An SD with a snorkle and no pin striping......lolz.