I would use either a black wooley bugger as a searching pattern, or a elk hair caddis if you want to fish a dry fly. As far as your fly being swept down stream, this isn't a bad thing. There's a technique called the wet fly swing which is basically casting up and across stream and letting your fly drift with the current until it is directly down stream from you. Depending on the current speed you may need to mend your flyline as it drifts down. Hope this helps.