Bring a pot of salted water to boil over high heat. Turn off heat, add shrimp, and poach until shrimp are opaque and just cooked through, about 2-3 minutes.
Drain shrimp and set aside until cool enough to handle, about 10 minutes. Chop shrimp into 1/2-inch pieces and place in a large, non-metalic bowl.
Add lemon juice, lime juice, tomato, red onion, jalapeno, cilantro, and salt to the shrimp. Toss to combine, cover and refrigerate.
Just before serving, dice avocado and add to the ceviche. Gently toss to combine.