Heat 1 inch oil in a large skillet over medium-high heat to 375 degrees F (190 degrees C).

Mix okra, onion, water, egg, salt, and pepper together in a large bowl. Combine flour, cornmeal, and baking powder in a small bowl: add to okra mixture.

Lower spoonfuls of okra batter carefully into the hot oil in batches. Fry on each side until golden, about 2 minutes per side. Transfer to a paper towel-lined plate to drain. Repeat with remaining okra batter.