Rinse fish under cold water and pat dry. Season both sides with salt and pepper. Heat oil in a large skillet over high heat. Add fillets and brown on both sides, 2 to 3 minutes per side. Remove and place on a serving plate. Pour off most of the oil left in the pan leaving only a coating. Add one tablespoon of water along with the onions and peppers and cook for about one minute. Add vinegar and sauté until tender. Pour over fish. Dish can be served hot, cold or room temperature.