Mix the vinegar, soy and honey thoroughly in a glass bowl.
For the Ginger, I always freeze my leftover ginger root and I find that actually makes it easier to work with. To get some great ginger taste, just scrape the peel off of the outside of the frozen ginger root with the edge of a spoon. Then grate the frozen ginger right into the bowl with a microplane grater. Add in the remaining marinade ingredients and combine thoroughly.
Clean and rinse the Mahi Mahi filets. I like to cut the blood line completely out of the fish because the kids don't like the more fishy taste it gives the meat, but that is up to you.
Pat the filets dry, place in a shallow dish and pour the marinade over the Mahi Mahi filets.
Place the dish in the refrigerator and marinade for at least 30 minutes, but no more than an hour (so I guess that makes it 45 minutes!).
The key to grilling fish is to cook it quickly over a really hot grill so you don't dry out the meat. So heat your grill to high.
If you have a fish basket, now is the time to break it out. Otherwise, make sure you REALLY clean and oil the grates of your grill with some vegetable oil. Nothing sticks quicker than fish and it's really kind of heartbreaking when you leave some of that delicious meat back on the grates.
Remove the filets from the marinade and place on the grill, reserving the marinade (we are going to use it later).
Grill the Mahi Mahi filets for 2 - 3 minutes on the first side and then flip them over and grill for an additional 2 - 3 minutes on the other side. These times are optional, but it is pretty easy to see when fish is done cooking. As the fish cooks through, the meat becomes more and more opaque. Remember though, don't overdue it!
Heat the remaining marinade on the stove and simmer until reduced slightly.
Drizzle a little of the sauce on the grilled Mahi Mahi filets and serve over rice. Amazing!