Bring salted water to a boil, add shells and cook for 10 minutes or al dente. Meanwhile, cook onion and peppers in oil, covered for 10 minutes or until tender. Add garlic, tomatoes, juice and thyme and simmer, uncovered for 5 minutes. Add zucchini and squash, cover and simmer another 5 minutes. Add seafood of choice and simmer, uncovered for 5 minutes or until cooked through. Season to taste with salt and pepper; spoon over cooked pasta.