In a deep skillet over medium-high heat, add 1½ tablespoons of oil.
Once the oil is hot, add the onions. Sprinkle with salt and pepper, then cook, stirring frequently, for about 2 to 3 minutes. Once the onion softens and is beginning to brown, transfer to a plate.
Add the remaining 1½ tablespoons of oil to the skillet and stir in the sliced okra. Cook, stirring occasionally.
Once the okra begins to brown, add the garlic and cook for another 2 minutes.
Return the onion to the pot, then add the tomatoes and cup of water. Sprinkle with salt & pepper and stir well to combine.
Bring the mixture to a boil, then lower the heat, cover, and simmer for about 45 minutes until the okra is tender and the stew has thickened.
Stir in the sliced sausage and shrimp. Cook until the shrimp just turns opaque and the sausage is heated through, about 5 minutes.
Remove the stew from heat and sprinkle with oregano and parsley.