Put the prawns in a bowl with the chilli, coriander leaves, the zest and juice of 1 lime, the sweet chilli and vinegar. Crush one half of the garlic clove, stir in and leave to marinate for 5-10 minutes.
Meanwhile, preheat the grill to medium high. Slice the ends off the ciabatta, then cut the loaf into 8 slices. Brush both sides of the slices with the oil, then rub the remaining garlic over each.
Put the bread on a baking sheet and toast under the grill for 2 minutes on each side.
Cut the remaining lime into wedges. Stir the rocket through the prawns and spoon on to the ciabatta toasts. Serve with the lime wedges to squeeze over.