Cook the shrimp: Bring a pot of salted water to a boil. Prepare a large bowl of ice water and set aside. Add the shrimp to the boiling water and cook for exactly one minute. Remove the shrimp from the pot with a slotted spoon and immediately add to the ice water to cool thoroughly. Drain and dry the shrimp a bit on paper towels then put them in a clean bowl.

Add the tomatoes, red pepper, onion, cilantro, jalapeño, and avocado to the shrimp. Season with salt and pepper and toss lightly.

Make the dressing: Finely zest 3 of the limes and juice 6 of them. Combine juice and zest in a small bowl and mix in horseradish, ketchup and olive oil. Pour the dressing over the shrimp and vegetables and toss. Check seasonings and adjust if necessary.

Garnish with extra cilantro and lime wedges.