In a blender, whizz the sweetcorn, along with any liquid from the can, into a rough purée and set aside.
Heat the oil in a large lidded frying pan and cook the onion for 2-3 mins to soften. Add the curry powder and garlic and cook for 1 min more until fragrant.
Tip the creamed coconut into the pan with 300ml water, stirring until the creamed coconut dissolves. Add the puréed sweetcorn and bring to the boil. Place the haddock fillets in the sauce, then reduce the heat to a simmer. Cover and cook for 20 mins, or until the fish is cooked through. Season and serve with rice.