Preheat fryer to 350 degrees F.
Cut the tough and fibrous bottoms off the asparagus and peel stems with a vegetable peeler. In a mixing bowl, combine flour, salt, and coriander. Whisk in soda water just until incorporated with the dry ingredients. Let the batter rest at room temperature for 1 hour. Dip asparagus in batter and place in fryer until golden brown, about 3 minutes.
Place on paper towels to drain and sprinkle with sea salt. Serve with lemon wedges.