Add shrimp and cook until pink and firm, about 5 minutes.
Remove shrimp from water with slotted spoon and place in large mixing bowl. Sprinkle with contents of taco seasoning mix and toss well to coat. Or, put shrimp in plastic bag with seasoning, close bag well, and shake to coat.
Serve warm, or refrigerate and serve up to 24 hours later.
For Tartar Sauce:.
Stir together mayonnaise, taco sauce and relish in small bowl.