They couldn’t, because fish is judgmental and constantly makes snide comments about dog’s personality, choices, etc. (Clearly Bernice is the fish in this story).
The fish won’t be able to breath oxygen, and the dog will die trying to breath oxygen with gills. Shannon leaves another wake of destruction in her path. That’s pretty on brand.
Wow, they actually said their own kids would be BETTER than Shannon. Saying the quiet part out loud? This may be the best Shannon story line ever.