Cook the pasta shells according to the directions on the package
While those are cooking, grab a large bowl, and mix the sour cream, mayonnaise, horseradish sauce, onion powder, garlic salt, and pepper
At this point...the sour cream mixture is so delicious, you'll want to dip some cucumber slices into it
When the pasta is finished cooking, drain, and rinse it
Add the pasta, and shrimp, cucumber, and celery to the sour cream mixture
Refrigerate for at least 30 minutes, or until you are ready to serve