In a medium pot, pour enough oil so that the oil comes 3 inches up the sides. Heat over medium heat until a deep-frying thermometer inserted in the oil reaches 180°C. (If you don't have a thermometer, a cube of bread will brown in about 3 minutes.)
In a large bowl, liberally sprinkle the rock shrimp with salt and coriander.
In a separate bowl, whisk together the flour, cornstarch, ginger ale and soda water.
In a separate dish, add the remaining flour and add the shrimp, tossing lightly to coat. Shake off the excess flour, and add the shrimp to the batter. With a wire spider or slotted spoon, add the shrimp to the oil and fry until light brown, about 2 minutes.
Lightly flour the lime slices, add the slices to the oil and fry, about 1 minute. When the shrimp is golden brown, add the parsley to the oil and fry until crispy, about 30 seconds.
Remove the shrimp, lime slices and parsley from the oil and place on paper towels to remove any excess oil. Season immediately with salt.Place on a platter and garnish with the lime wedges.