Heat the olive oil in a skillet over medium-high heat; cook and stir the garlic in the oil until golden brown, taking care not to burn the garlic. Add the tomatoes and mix well until they release their juices. Stir in 1 teaspoon oregano.
Place the cod and shrimp on the tomato mixture; season with salt. Cover skillet and simmer 3 minutes. Flip the cod and season again with salt and 1 tablespoon oregano; re-cover and cook another 3 minutes. Remove the cover and allow to cook until the juice evaporates slightly, 2 to 3 minutes.
