Heat a Dutch oven over medium-high heat. Coat pan with cooking spray. Add oil to pan, swirling to coat. Add leek; sauté 8 minutes or until tender and lightly browned. Add garlic; sauté for 1 minute. Stir in 2 1/2 cups water, wine, tomatoes, and thyme; bring to a boil. Cover, reduce heat, and simmer 20 minutes. Discard thyme.
Stir in salt, pepper, shrimp, and grouper; simmer 6 minutes or until fish is done. Remove from heat; stir in parsley. Serve immediately.