How to Make It
In a glass bowl, combine the lemon juice, lime juice and jalapeño. Pour 1/3 cup of the marinade into another glass bowl and set aside. Add the snapper to the large bowl and mix well; cover and refrigerate for 2 to 4 hours, stirring occasionally.
Meanwhile, bring a large pot of salted water to a boil. Add the shrimp and cook just until pink and firm, about 2 1/2 minutes. Drain and let cool. Add the shrimp to the marinade in the small bowl and toss well. Cover and refrigerate for 2 to 4 hours, stirring occasionally.
Drain the snapper and transfer to a medium bowl. Mix in the onion and cilantro.
To assemble, arrange 2 mango strips on a slice of jicama. Top with 1 tablespoon each of the guacamole and snapper seviche. Roll the jicama around the seviche to form a tight cylinder and garnish with a shrimp. Repeat with the remaining ingredients and serve at once.