Any fishing experts here?? HOW DO I FISH?

My teacher (Marine Bio) took us fishing in brackish water. What he did for bait was, he took canned sardines and mixed it with flour ( as a filler.) It became this fishy dough that was easy to plant on the hook. And even I, as a terrible fisher, could even catch loads of fish with it. Because saltwater and freshwater animals are different, they might not recognize a bait from the wrong habitat ( I assume.) Hope this helps!