You already know that fish is very good for you, and that omega-3 fatty acids, the healthful compounds in it, are all the rage. But do you know why? Here's what omega-3s do:

* Reduce the risk of heart disease. These amazing little polyunsaturated fatty acids reduce blood viscosity, making it less likely to form clots, thus reducing the risk of sudden death. They also lower lipid (blood-fat) levels.

* Help prevent life-threatening arrhythmias (interruptions in the heart's rhythm) by stabilizing the heart's muscle cells.

* Alleviate rheumatoid arthritis pain by reducing stiffness and joint inflammation.

* Fight depression by enhancing mood. They help keep the fatty membranes around brain cells fluid, which makes it easier for messages to be transmitted (including those triggered by serotonin, a mood-regulating chemical).

Fish is the best source of omega-3s (especially fatty fish, like Atlantic and sockeye salmon, mackerel, bluefish, halibut, herring, tuna, sardines and striped bass), but leafy greens, nuts, canola and soybean oil, tofu and flaxseed also provide omega-3s in small amounts. (Shellfish offer a small amount, plus all varieties of crustaceans are loaded with zinc, a mineral that ensures proper vitamin metabolism and enzyme activity in every organ in the body.) Seven to 10 ounces of fish a week (2-3 servings) is enough to reap good-health rewards. With these nutritious, easy-to-fix fish entrees you'll be "goin' fishin' " a few nights a week.

Fish sticks

Toss together these simple fish marinades and start licking your lips.

For light fish (such as flounder, red snapper, sea bass, trout)

* White Wine With Thyme: 1/2 cup dry white wine, 1 tablespoon drained capers, 1 teaspoon chopped thyme.

For firm-fleshed fish (like tuna, swordfish)

* Soy With Peppercorns: 1/3 cup soy sauce, 2 teaspoons tri-color peppercorns, cracked with mortar/pestle or heavy frying pan.

* Honey-Dijon: 1/4 cup water or white wine, 2 tablespoons each honey and Dijon mustard, 1 teaspoon grated ginger (or 1/4 teaspoon dried).

For shrimp

* Pineapple-Brown Sugar: 1/2 cup pineapple juice, 1/4 cup crushed pineapple (canned in water), 2 tablespoons light brown sugar.

For shellfish

* Coriander-Lime: 1/3 cup fresh lime juice, 1 teaspoon ground coriander, 1/2 teaspoon grated lime zest.

* Citrus-Chili: 1/2 cup orange juice, 1 teaspoon each chili powder and ground cumin.