Mix all the marinade ingredients in a large bowl. Add the fish and peppers, season well and toss to coat evenly. Cover and marinate in the refrigerator for 1–2 hours.
Preheat a grill or barbecue until hot. Thread the fish and peppers on to 8 metal skewers and grill for 4–5 minutes on each side until the fish is just cooked through. Serve immediately, garnished with chopped coriander and mint, with lime wedges for squeezing.