Preheat the oven to 400 degrees F. Slice each zucchini in half, lengthwise. Using a metal spoon or melon baller, hollow out the center of each zucchini. Place zucchini in a baking dish and set aside.
Warm the tablespoon of olive oil in a large skillet over medium heat. Add the garlic and allow it to heat through for 2-3 minutes. Add the spinach and gently stir for 3-4 minutes until spinach has wilted. Remove from heat.
Place the ricotta cheese, 1 cup of the shredded mozzarella, the parmesan, salt and pepper in a large bowl and stir to combine. Add the cooked spinach and incorporate into the cheese mixture.
Spoon the filling into the zucchini boats. Evenly spoon on the marina sauce and top with the remaining ½ cup of shredded mozzarella cheese.
Cover the baking dish with foil and bake for 30 minutes. Uncover and bake for an additional 5 minutes.