Mix together the black pepper, garlic, limes, green onions, yellow onions, Scotch bonnet peppers, half the pineapple, the coconut milk and bell peppers in another large shallow bowl. Add the fish and massage the mixture into it. Make sure to squeeze all the ingredients together to use all the flavorful juices. Let sit for 20 minutes at room temperature.
Preheat a grill to medium-high heat.
Grill the fish for 4 to 5 minutes, then gather the marinade and squeeze half of the juices and veggies in and on top of the fish. Flip and cook for another 4 to 5 minutes, and continue to squeeze and drizzle the remaining juice and veggies on top of the fish as it cooks. Finish with a squeeze of the reserved pineapple slices and serve immediately.