Yes, I have. If you wade out from the water treatment plant, you have slippery, but firm bottom,
If you wade out from the Water Street lauknch ramp, bear to the left, toward the anchored sailboats and you should find the same.
If you go straight out from the ramp, there are some soft spots but you shouldn't get stuck in any of it.
It will pay to bring a compass as fog can roll in and you can lose your bearings pretty quickly. A few years ago, I had a friend who went out there without a compass and would have returned via Plum Island, if the water hadn't been too deep.
My friend Steve (SCKFish) fished Joppa with Riddler in kayaks a couple days ago and took a 46' fish on light spin tackle.
StriperSurf Fly Fisher