I agree with fejjys thoughts. Look for higher salinity near the mouths, and dont worry about visibilty. The baitfish will be at the mouths.
I still think everyones underrated the el nino effect of temp changes in offshore currents.The slightly lower water temps in the rivers, means that the feeding triggers have not yet started in the mature jacks. I reckon they slow down their metabolic rate and dont need to feed as often. If Im right, we will see more smaller jacks caught in the 35-45cm range as the water temp improves, as the smaller fish need to feed more often to sustain growth rates. The bigger fish dont need to feed as often. The only way to entice these dormant big boys to play, is to get a reaction bite when something is right in front of his nose, so lures might win out over bait, for a change?
So I reckon jacks are still sitting in thier usual hangouts, they just arent hungry.
Just a theory.
cheers
Andrew