This type of marinade is used just before the item is to be cooked. The food is not soaked in a liquid; it is just lightly moistened with oil and an acidic element, such as lemon or wine, and gently flavored with aromatics. This method is used when you wish the item to be cooked to be lightly flavored.
For fish: Prepare the fish as for cooking and place it in a nonreactive dish. Sprinkle with a bit of oil (vegetable or olive) and fresh thyme to taste, then add lemon slices and a couple of bay leaves.