Make sure shrimp is peeled and deveined. I slice shrimp in half and place in a bowl. Squeeze all limes until shrimp is almost covered. I add a little water to cover shrimp and mix. Place in fridge for about 30-40 mins, shrimp will change color when fully cooked from the lime. While shrimp is “cooking” boil tomatillos. Then blend serranos, jalapeños, cilantro, garlic and tomatillos. Add blended mixture to shrimp once shrimp is fully”cooked”. Add sliced onions, jalapeños, cucumbers and cubed avocados. Mix and season with salt. I place in fridge for about 20mins to let everything marinate together. Serve on tostadas or eat with crackers!