The acidity of the lime juice in this coastal dish changes the proteins in the fish, essentially “cooking” them without heat.
Fill saucepan with water, and bring to a boil over high heat. Add ¼ cup salt and shrimp and immediately turn off heat. Let the shrimp sit until cooked through – or about 3 minutes. Drain.
Cut raw fish and shrimp into ½ inch pieces.
Place the fish and shrimp in a glass or ceramic casserole dish and cover completely with the lime juice. Allow to marinade, stirring often, in the refrigerator for 3-4 hours.
Pour off most of the lime juice, allowing the fish and shrimp to remain moist.
Add the onion, tomatoes, green peppers, jalapenos, green olives, cilantro, ½ tsp salt, pepper, oregano and cayenne. Add in the orange juice and toss well. To serve, line individual bowls with lettuce leaves and garnish with avocado slices. Provide warm corn tortillas on the side.