Cook okra in 2 tablespoons butter in a large skillet over medium-high heat, stirring constantly, until lightly browned.
Set aside.
Combining remaining 1/4 cup butter and flour in a large Dutch oven; cook over medium heat, stirring constantly, until roux is chololate colored (20 to 25 minutes).
Stir in green onions, celery, and garlic; cook, stirring constantly, until vegetables are tender.
Add okra, water, and next 6 ingredients.
Bring to a boil; reduce heat, and simmer, uncovered, 2 hours, stirring occasionally.
Peel and devein shrimp; add shrimp and crabmeat to okra mixture.
Simmer an additional 10 minutes, stirring occasionally.