I call them jig flies. More jig than fly. But as long as you aren't in a fly fishing only area, who cares? (besides the 'purists'...)

The bad part about them is that they can be used as a effective snagging tool. But then so can just about anything that has a hook.

But as you noted, it's that swimming action that sets them appart.

You could fish them below a big 'strike indicator', but then why bother fly fishing? Just get a spinning rod and west coast float and jig fish for real...

There are a few sitiuations where these jig flies really shine in my experience (I fly fish and jig fish, and have often combined both approaches like this)...

Slow deep pools \ back eddies:

Cast out, let sink a little, strip in 6 - 10 inches, let sink, strip, sink, etc. The jig fly will rise and fall and drive the fish crazy. Experiment with jigging as you are stripping. You can start at the surface and them work it allong the bottom. Just don't lift the rod too fast or strip to fast. Just a gentle motion is all that is needed. Eventually you will be able to tell the difference between a rock, log, fish belly, or fish mouth juist by the feel and at what point you feel the 'bite'. Most takes will be as the jig fly is sinking, so as soon as you strip or lift the rod tip, you'll feel resistance. If questionable, I do a test strike by just pulling a little to see if I get a head shake. If I feel a headshake, I set the hook hard. If not, I gently tug until it frees up from whatever it was hung up on or rubbing against.

The other time I really like them is when working a nice run that has a good current seam. Then I either high stick nymph fish the jig\fly down the fast side, or try more of a classic drift and swing approach, then at the end of the swing you can let it hang for a second, then raise and drop it - allowing it to free fall 4-10 inches and just dance up and down. Strip in a few feet and repeat.

In both water types, I've had steelhead and salmon go crazy for it. Coho love it the most as do pinks. My top jig\fly has been a big cerise or hot pink fly. I've taken SRCs, Dollies, Coho, Steelies with that jig\fly.