Preheat the oven to 350°F (175°C).
In a large skillet, sauté garlic in a bit of oil until fragrant.
Add shrimp, scallops, and white fish to the skillet; cook for about 5 minutes until just opaque.
Stir in heavy cream, lemon juice, cooked rice, parsley, and season with salt and pepper.
Transfer the mixture to a greased casserole dish, flattening it into an even layer.
Top with cheddar cheese and breadcrumbs, then drizzle a little olive oil over the top.
Bake for 25-30 minutes, or until the top is golden and bubbly.
Let the casserole rest for about 10 minutes before serving.