Oh, Mr. MuchDutch, thank you! I admit I was sitting on this curb, dejected, with the remains of my burst bubble wondering what would become of me... When you stopped by this thread, it really cheered me up!
I intentionally didn't put a lot of specifics into the first post to see what it might reveal. I wasn't clear enough and that confused swmnwdsfishes.
What I am looking for is indeed a use of the venturi principle in water (which we know works) -- like the eductors in reefkeeping, or ring injectors in carburetors.
Instead of the design goal being maximum output velocity or maximum mixing of different fluids via turbulence, I would like to maximize the suction volume vs. the driving fluid volume:
Imagine the above nozzle as a ring with a pass-through middle, like these carburetor boosters but with apertures designed for the properties of water and creating a low Reynolds number after the water-water boundary:
The goal isn't the 15x claim for the air fan. For this application I'd be content with 1.5x in water.