In a pot, put lemon juice, garlic, bay leaves, peppercorn and salt, then fill with water to halfway. Bring to a boil over high heat. Stir shrimp into boiling water, then turn off heat.
Allow shrimp to poach until they are no longer translucent in the center, about 3-5 minutes. Drain using colander in the sink, and place shrimp on a baking sheet and refrigerate until cold.
In a non-metallic bowl, stir coconut milk, lime juice, serrano chili pepper, chopped cilantro, and onion together. Season with salt and/or pepper to taste.
Cut chilled shrimp in half lengthwise and stir into the coconut marinade. Cover and refrigerate before serving. Garnish with cilantro and lime wedges.