Aguachile Verde is made from fresh shrimp, serrano peppers, garlic, cucumber, and red onion with a splash of fresh lime juice.
Make sure you clean well the shrimp and devein, and after that pat dry with paper towels. Set aside in a large bowl.
Add the lime juice, some salt, and the onion slices. Toss to combine.
Cover the bowl and refrigerate it for 20-30 minutes.
Remove from the refrigerator and drain the accumulated juice from the shrimp and onions, into a small bowl and set aside.
Add half of that mixture to a blender with the garlic, pepper, salt, serrano pepper, cilantro, a few pieces of the onion that were marinated, and about 2-3 tablespoons of the chopped cucumber. Blend well until smooth.
Add the remaining lime mixture and the blended mixture to the bowl with the shrimp. Mix well and adjust for salt and pepper and lime if needed.
Add the remaining cucumbers and avocado slices and serve cold with tortilla chips.