Heat the oil in a frying pan, add the garlic and rosemary, fry for 30 seconds, then add the fish.
Cook for 3-4 minutes per side until done, take it out and pour off the excess oil.
Brown the floury bits left in the pan (add 1 tbsp flour if there's too little), pour in the vinegar (stand back, the steam is strong), then the water, and stir into a sauce.
Spoon the sauce over the fish and serve with Greek salad.