Lay the scallops on a plate and with a couple of paper towels press down gently to remove excess moisture. Cut into quarters and transfer to bowl, set aside.
In a large glass bowl, add the red onions and all of the juice from both the lemons and limes. Add the scallops to onions and stir gently.
While the scallops cook and onions marinate, prep the rest of the ingredients, leaving the avocado for last.
Add ingredients to bowl and you chop, but wait to mix in until done with all chopping. Season with salt to taste. Stir well to combine. The scallops only take 20 minutes to cook in the citrus juices.
Fold in the avocado, serve with saltine crackers or tortilla chips. Yields 6 servings for an appetizer.