Preheat your oven to 375°F (190°C).
In a saucepan, melt butter over medium heat and sauté garlic until fragrant.
Add shrimp and cook until pink.
Stir in crab meat and chopped spinach, cooking until spinach is wilted.
In a large mixing bowl, combine cream cheese, sour cream, and half of the Parmesan and Mozzarella cheeses.
Mix thoroughly.
Add the seafood mixture to the cheese mixture.
Stir until evenly combined.
Transfer the mixture to a greased baking dish.
Top with the remaining cheeses and bake for 25 minutes until bubbly and golden brown.