Bring a medium pot with salted water to a boil, then turn off the heat.
Add the shrimp to the hot water. Let the shrimp sit in the water for about 3 minutes, or until it turns pink and is cooked through. Meanwhile, prepare a bowl of ice water.
Remove the shrimp from the water with a slotted spoon and immediately plunge it into the ice water to prevent overcooking.
Place shrimp in a large bowl. Add the lime juice, sea salt, and black pepper.
Cover and refrigerate for at least 30 minutes, until it has turned pink, or for up to 8 hours.
In a large bowl, stir together the red onion, cilantro, tomato, jalapeno, sugar-free ketchup, hot sauce, lime juice, salt, and pepper.
Gently fold in the avocado and cooked shrimp. Serve with chips, crackers, or veggies. Alternatively, you can serve the Mexican shrimp cocktail by dipping the shrimp into the sauce instead.