I have used the Hydroforce nozzle (3") and I've found it to be very effective. I love the thing, because it gives me the flexibility to do "normal" underwater dredging but also allows me to dig into dry areas and still move materials.
Using the Hydroforce does turn a "dry" area into a "wet" area, though, so I'm not sure if that's what you were looking for.
As an example, I posted this video from a couple years ago of using our Hydroforce up in New Hampshire. (That's my son running the nozzle). You'll notice that the area where we've punched our hole was dry to start, but as we worked our way down through the material the hole filled in with water - because of the Hydroforce and also simply because we got down to the water table/level.
And in this video (down in Virginia) you can see that we've worked our way into the dry area of the creek bed (always staying below the high-water line).