For Spotties at Palm Beach Reef, I set them 10ft under a piece of styrene, never used a ballon !
If there is a little current going, no balloon or float, just keep adjusting the length of line from mid water to deeper and deeper, maybe even have a couple out.
Maybe even have a 10ft leader and put on a 10 ball sinker.
It really depends on where they are feeding !
8)