This is what I do with halibut quite often...
First, I make a simple court bouillon. I mix equal parts water and white wine, add some salt, whole peppercorns, crushed garlic, parsley, and a bay leaf or two. I heat it to just below boiling -- with a lid on so it doesn't evaporate -- and let it brew for a while to infuse the liquid with all those flavors. Use enough liquid to poach the fish. And regarding the liquid, you can use just water, or all wine. I happen to like the 50/50 mixture.
Second, I make a green sauce from Alice Waters's book "The Art of Simple Food" with 1/3 cup of chopped parsley, 1/2 cup of olive oil, a couple of finely minced garlic cloves, a tablespoon of minced capers, and the zest of one lemon. The capers should provide plenty of salt, but you might want to add some depending on your palate. Let it sit for a while at room temperature for the flavors to marry (ideally overnight).
Then just poach the halibut in the court bouillon and serve it with that green sauce when it's done. For a 1-inch think fillet I generally poach for 9 - 10 minutes.
Any leftover green sauce will keep in the fridge for quite a while (up to three months I have heard), and I also freeze the court bouillon for a second use (but no more than a second use).