Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine cream cheese, sour cream, and mayonnaise until smooth.
Add chopped spinach, cooked shrimp, crab meat, mozzarella cheese, and Parmesan cheese to the bowl.
Season with garlic powder, cayenne pepper, salt, and pepper.
Transfer the mixture to a baking dish and spread it evenly.
Bake in the preheated oven for 25-30 minutes or until bubbly and golden brown on top.
Remove from the oven and let it cool for a few minutes before serving.
Serve warm with tortilla chips or fresh vegetables.