Preheat oven to 200 degrees F. In a large saucepan, heat 1 1/2-inches of oil to 375 degrees F. Pat squash rings dry with paper towels. Place squash rings in a large resealable plastic bag. Add 1/2 cup flour, seal bag, and shake to coat.
In a large bowl combine 1 cup flour, cornstarch, jerk seasoning, and salt. Whisk in water. Fold in ginger beer until smooth.
Working in batches of 4 or 5, dip squash rings into batter and add to hot oil. Fry 2 to 3 minutes or until golden brown. Remove to paper towels to drain. Sprinkle with additional salt. Return oil to 375 degrees F between batches. Keep squash warm in the oven on a baking sheet while frying remaining slices. Serve hot with spicy BBQ sauce.