Mike F:
I can cast and keep the flies of rocks just fine. However this weekend I was deliberately drifting flies in at the base of the rocks and letting them bang around in the white water at the jetties edge. It was almost a vertical fishing situation as opposed to a cast and retrieve.
Having thought about it a bit I think I understand why Ray Bonderow who does a lot of rock/cliff fishing advocates an intermediate line w/ sections of lead core built into the leader and standard unweighted flies. I use that approach in winter creek fishing and it might work better on a jetty than a sinking line.