Our friend Kathy Cavanaugh shares this family recipe for grilled swordfish:
I learned this technique from a couple of my uncles.
Take Hellman's mayo (and only Hellman's!). I usually add minced garlic and either lemon or lime juice and zest to the mayo—eyeball the amounts depending on taste and to make a fairly thick sauce.
Slather both sides of the swordfish with the mixture. Eyeball the amount, use enough to coat the fish. Then grill over charcoal until the fish sweats" (+/– 7 minutes per side, depending on thickness).
The mayo seals in juices, but you won't even see or taste it on the fish when it's cooked.