not only can it be thermoclines but shadows, foamy bubbles from wave action,current (rips) and rock formations....something that gives a predator fish the "edge" where they can see the bait but the bait cant easily see them....even if its only momentarilly ....and bright sunLIGHT is avoided because fish have no eyelids. Fish have an optimum temperature they prefer and will always gravitate to that depth. Of course they still have to follow pods of bait or cruise long distance until they find food.
When you think of it like that it becomes more of a science.
NilsC
is great at reading water and understanding the underwater environment and how things like sandbars help bass coral baitfish for ambush. Find the bait...and you'll find the fish.
