Prefixes sub- and super-

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Across
  1. 2. pay part of the cost of producing something to keep the selling price low
  2. 6. regions adjacent to or bordering on the tropics
  3. 8. (of water) go down to a lower or the normal level
  4. 9. arrangement to receive something regularly by paying in advance
  5. 12. to be under water
  6. 14. vessel used under the sea
Down
  1. 1. person who directs or oversees work or an activity
  2. 3. under the earth
  3. 4. an extremely famous and successful performer or sports player
  4. 5. being above or beyond what is natural
  5. 7. having or showing exceptional ability or powers
  6. 10. large self-service shop selling foods and household goods
  7. 11. a residential district located on the outskirts of a city
  8. 13. underground road or railway