Thaw and peel Shrimp. I slice the shrimp into 3 pieces. You can leave them whole if you want.
Chop red onion into small pieces. Deseed and chop serrano chilies into small pieces. Chop fresh garlic into small pieces. Chop 1 cup Cilantro leaves.
Add all ingredients (except cucumber)to a gallon zip-lock bag. Add the juice of 6 lemons and 6 limes. Seal and place flat in the refrigerator for 3 hours or overnight. NOTE: The acid from the citrus will cook the shrimp. You will notice the shrimp will start to turn pink. I prefer to place it in the refrifgerator overnight.
Deseed and chop 1 cucumber. Add 1 can of tomatoe sauce and add to mixture and place back in the refrigerator for 1 hour or until ready to serve. Before serving sprinkle with salt and pepper to taste.