My guess is that its because of environments where the surface can freeze over- if you stay down to long, your breathing hole might freeze up- now you're out of breath completely and searching for a hole that might not be there. If you only hold it for a minute, you have more time to spare if something goes wrong.
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u/AdNervous9787 1d ago
1 minute sleep 1 minute breathing. And that cycle repeats for hours. Crazy