What is the riddle?

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Across
  1. 2. opposite of water
  2. 4. the past tense word of will
  3. 6. a small sea-life creature with gills and fins
  4. 7. this word is used to talk about a person without a gender
Down
  1. 1. opposite of off
  2. 2. the word "live" in past tense
  3. 3. the 9th and 6th letter of the alphabet combined.
  4. 4. who, what, when, why. What's missing?
  5. 5. the tense version of "lived"