How long on average can a killer whale stay underwater without coming up to the surface of the water?

Question: How long on average can a killer whale stay underwater without coming up to the surface of the water?
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Asked by AB+SW to Lauren on 11 Mar 2016.
- Lauren Laing answered on 11 Mar 2016:
  
  This is roughly 20 minutes! This means a killer whale can leisurely swim for about 5 kilometers before it must come up for another breath of air.

Question: How long on average can a killer whale stay underwater without coming up to the surface of the water?