Rub salt all over the mahi-mahi fillet.
Heat-up the grill then grill each side for 3 minutes.
Meanwhile, combine water, vinegar, whole peppercorn, garlic, and sugar in a cooking pot. Let boil. Adjust the heat to low.
Put-in the grilled mahi-mahi and long green chili then continue to cook (covered) for 12 to15 minutes. Add more water if needed.
Transfer to a serving plate.
Serve. Share and enjoy!