How to Make It
Squeeze juice from 2 lemons into a small bowl and set aside, reserving 2 squeezed halves. Combine 3 tablespoons lemon juice, sugar, salt, coriander, reserved lemon halves and 6 cups water in a large saucepan. Bring mixture to a boil, stirring occasionally to dissolve sugar and salt. Add shrimp to boiling water and cook, uncovered, until just cooked through, about 3 minutes. Remove from heat and add 8 cups ice to saucepan. Let shrimp sit in liquid until cooled completely, about 10 minutes.
Meanwhile, combine ketchup, horseradish, Worcestershire, vinegar, 1 tablespoon remaining lemon juice, and sriracha in a small bowl, stirring to combine. Slice remaining lemon and serve with cooled shrimp and dipping sauce.