Acqua pazza, or 'crazy water' is the humorous term for an extremely easy, but tasty way to poach fish--or, more specifically, to the poaching liquid. You start with an oil and garlic base, as if you were making an ajo e ojo, in a pan wide enough to fit your fish filets in a single layer. Then, letting the oil cool a bit, add cherry tomatoes (pomodorini 'pachino'), which you can split in two if they are fairly large, chopped parsley and a generous splash of white wine. Place filets of a white-fleshed fish (today I used Chilean sea bass) into this 'bath' and add enough water (or fish broth) to come about halfway up the fish. Season with salt and pepper and sprinkle with some more parsley. Cover and allow to simmer gently until the fish is cooked through, about 10-15 minutes, depending on the type and thickness of the fish.NOTES: The version described above is about the most basic version of this dish. For more complexity, you can add olives, capers and/or anchovies to the acqua pazza. If you like some heat, add a bit of peperoncino (or red pepper flakes) to the hot oil along with the garlic.
There also exist more 'refined' versions that start with a soffrito including, in addition to or instead of the garlic, onion, carrot and celery. Some recipes also call for the addition of bay leaf and other herbs to the poaching liquid.
The type of fish is yours to choose, but white-fleshed fish work best. Orata (sea bream) is probably the most typical fish used for acqua pazza, but merluzzo (fresh cod), scorfano (red fish), rombo (turbot) and spigola (bass) are often used--even sgombro (mackerel) although personally I'm a bit dubious about this last option.
You can also make whole fish all'acqua pazza if you like--in fact, this is the original way to make it. If you do, you will have to turn the fish over during cooking to make sure it cooks fully on both sides. With filets, assuming that they are not too thick, this may not be necessary.
Done and ready to serve...