Place the shrimp in a large bowl and add the lime juice. Measure in the ketchup, hot sauce, Worcestershire, onion and cilantro. Mix well.
Cut the avocado in half, running a knife around the pit from stem to blossom end and back again. Twist the two sides apart and scoop out the pit. Scoop each half out onto your cutting board, cut gently into small cubes, then scoop the avocado on top of the shrimp mixture. Carefully fold in the avocado, then divide the mixture between 4 to 6 serving dishes (martini glasses make a dressy presentation). Garnish with sprigs of cilantro and prepare for a taste of beach-side dining.