Heat a barbecue or chargrill pan to high heat.
For jerk spice paste, pound chillies and garlic to a paste with a mortar and pestle, then stir in remaining ingredients and 1 tsp sea salt flakes.
Slash fish a few times each side, then rub all over with jerk spice paste. Drizzle with oil, then barbecue, turning carefully every few minutes, until fish has a nice crust and is cooked through (about 15 minutes). Transfer to serving plates and keep warm.
Meanwhile, for pineapple-lime salad, combine ingredients in a bowl, season to taste, drizzle with olive oil, and serve scattered with coconut alongside fish.
