Preheat your oven to 375°F (190°C).
Cook lasagna noodles according to package instructions. Drain and set aside.
In a mixing bowl, combine ricotta cheese, 1 cup of mozzarella cheese, and ½ cup of Parmesan cheese. Set aside.
In a saucepan, heat olive oil over medium heat. Add minced garlic and cook until fragrant.
Add crab meat and shrimp to the saucepan. Cook until shrimp is pink and cooked through. Remove from heat.
Spread a thin layer of marinara sauce on the bottom of a baking dish.
Layer 4 lasagna noodles over the sauce. Spread half of the ricotta mixture over the noodles. Add half of the seafood mixture on top of the ricotta. Pour a third of the marinara sauce over the seafood.
Repeat layers: noodles, ricotta mixture, seafood mixture, and marinara sauce.
Top with remaining noodles, marinara sauce, and sprinkle with remaining mozzarella and Parmesan cheese.
Cover with aluminum foil and bake for 30 minutes. Remove foil and bake for an additional 15 minutes or until cheese is bubbly and golden.
Let lasagna rest for 10 minutes before serving.