Place a piece of greased heavy-duty foil over the grate. Using a sharp knife, poke holes or make slits in the foil to allow the drippings to drain away from the fish or seafood.
When it's time to turn the food, use grill tongs. That way you can turn the fish or seafood without piercing the surface and releasing flavorful juices. If tongs are not among your supplies, use a wide metal spatula. Just slip the spatula between the food and the foil, then turn.
Improvisation is a necessary tool for all outdoor chefs, and you can't find that at your local hardware store!