Mahi-mahi, also called dorado or dolphinfish (Coryphaena hippurus), is a fast-growing tropical game fish prized for firm, lean, mildly sweet pale flesh that grills beautifully. Alive in the water it is one of the most spectacular fish in the sea — electric blue-green along the back, brilliant gold down the flanks, flickering with colour as it hunts at the surface — and that vivid, athletic fish becomes a clean, large-flaked white-fleshed steak that takes a char and a marinade as readily as any fish in the kitchen.