
All you need is some marinade, bacon, toothpicks soaked in water, some foil, and BBQ sauce.
Guarenteed to be a hit.

Then, using the wet toothpicks (so they don't burn in the BBQ) to hold the bacon in place, wrap bacon around the tuna loin, completely covering the fish.

Use foil to catch all the oil - tuna is very rich and there will be alot of oil!
Also, BBQ the fish while cooking the crab you just caught - highly recommended as a side dish.

And it will help clean up the BBQ sauce all over you.
No advice on what to tell the hungry family when the fish is gone - they won't believe anything you say.
Enjoy!