In a turbulent river it doesn't just float to the surface immediately.
No, not really Matt, it doesn't.
I mix my flavours in with the water that I mix the groundbait with and apply it with a spray bottle. I am pretty sure that all of the flavour is absorbed by the bread crumb so little is free to float to the surface.
If a turbulent river then I would probably add a lot of PV1 or other binder to get my ground bait down to the bottom, that said however, I rarely ever fish really turbulent rivers.