Although this is not a tidal water fly, it could very well be used in brackish water for bass or panfish. I suspect in appropriate colors, it could also work as a Bonefish or Redfish fly.
I originally tied it about 18 years ago, for both trout & bass. It was tied on a streamer hook, Mustad 9672, or 79580 in sizes from 10 to 2 to imitate large Stonefly nymphs and Hellgrammites, but I got away from tying it in any size but 2. The hook in the picture is a size 2 that I purchased from Togen's Fly Shop http://www.togenenterprises.com/home.html in Canada. It's a black nickel finished hook, and works well for bass flies. I like it particularly for this fly, which I primarily use in streams for Smallmouth bass. Togen's originally sold it as a Salmon/Steelhead fly hook, but now they call it a Black Nickel Curved Shank Hook. It's only available in size 2.
I now prefer this hook because it tends to ride inverted with the point up, making it snag much less than with other hooks.
Hook: Togen's Black Nickel Curved Shank, size 2
Thread: Black ( I use Danville Flat Waxed Nylon)
Bead: Tungsten, or Brass
Tail & Legs: Silicone or rubber
Under Body: Rabbit Dubbing ( black, olive/black, olive) Hareline makes some great dubbings, such as Haretron that can be used.
Ribbing: Transparent black vinyl, something with a rounded surface. ( originally Swannandaze)
Thorax: 2 wraps of Estaz. Opalesccent black, or olive
Wrap the dubbing by whatever method you prefer, and pick it out between the ribbing wraps with a bodkin to give it a buggy appearance.
This is a fairly simple & durable pattern, that could be tied in other colors as well. I originally tied it in black, olive, amber, & rootbeer.
Dead drift it with an up & across current cast, or impart some added motion with short strips. Vary your retrieve until you find what they want.