Heat 2 tablespoons oil in a large nonstick skillet over medium-high heat. Season shrimp with pepper and 1/4 teaspoon salt. Put 1/2 cup flour on a plate. Combine remaining 1 1/2 cups flour and seltzer in a bowl; mixture should be lumpy and thin.
When the oil is hot, dredge the shrimp lightly in flour, tapping to remove excess; dip the shrimp in seltzer batter. Add shrimp to skillet without crowding (work in batches, using remaining 1 tablespoon oil); cook, turning shrimp once or twice, until lightly browned and cooked through (about 5 minutes total).
Remove from skillet with a slotted spoon, and drain on paper towels; sprinkle with remaining 1/4 teaspoon salt. Serve with lemon wedges and snow pea salad.