If you are trolling for tuna, create a scenario below the boat that attracts fish to swim up behind it and eat, so they will be enticed to swim up. Use the bottom of your boat as a bait ball and run your tuna trolling lures behind it so that they appear to be squid that have gotten separated but are attempting to get back together. Because it appears to be an appealing opportunity, the tuna will swim up and feed on your lures.