This little bit of video is of shooting a mangrove jack in some deeper water. When chasing Jacks i have found that eye contact along with body language is a major playing factor when trying to close distance between yourself and the fish.
These fish are smart compared to say kingfish. Once eye contact is made i find that they tend to quickly create distance form the diver.
I have found that when chasing jacks if i try to use peripheral vision plus swim slowly and try to relaxed that i tend to be able to close some distance between the fish and myself allowing for a quick and clean shot.