Yes, we make PK a couple of times per year.
Hell's Gate isn't really one of the best places on the lake to dive, unless you're looking for "treasure" (items that have been dropped overboard and lost by party-boaters). Better spots are nearer the dam (although you must stay out of the restricted zone, so be careful), perhaps Governor's Cove or the nearby vicinity. I also enjoy diving along the wall near lake marker 12, and there's a little cove near marker 18, too, that is usually fair. Generally, the farther "upriver" you go, the more visibility suffers. Also, on my last trip there, we found that if you dropped below the first sharp thermocline, vis opened up quite a bit. We were near the north opening of Hell's Gate cove and went down to about 45 feet. The first 25 feet or so was typically low vis, about 5-8. Once we got below the thermocline, vis was well over 20 feet but, naturally, it was VERY cold, probably about 58 degrees.
Have fun exploring around for good spots!