Bring 1 gallon water to a simmer in a large stockpot. Add the salt, bay leaves and lemon juice. (The water should taste salty like the ocean.) With the water at a playful bubble, add the shrimp and poach until barely cooked through, 2 to 3 minutes. Drain and allow to chill in the refrigerator.
Whisk the ketchup, orange soda, clam juice, hot sauce, lime juice and pepper to taste, if using, in a medium mixing bowl.
Serve the cocktail sauce in a chilled glass bowl or individual cocktail glasses. Perch the shrimp and some lemon and lime rounds on the rim. Top with the avocado and cilantro. Serve with crackers.
The shrimp and cocktail sauce can be prepared up to a day ahead.