fish out of water a little mermaid story

It started out great. The MC was fantastically straight forward with his goals. The story was entertaining and a had a good pace. Although it had a few grammatical mistakes here and there, it was still legible. My main issue with the novel was that creatures specifically water based creatures like fish, turtles, and mermaid-like humanoids called Aquarians had a weakness to fire. No other type of creature up to that point were given a weakness nor were the weaknesses or resistances explained. The Aquarians literally suddenly swooped down from the sky on flying creatures. Does that make sense? They're literally fish people and the setting was set next to the sea, but I digress. My main issue the novel was that fire was extremely effective on Aquarians and any other water based creature. I knew that this wasn't Pokémon and that maybe in that situation they were fish out of water. However water magic does exist and it's common sense that water beats fire. Later on the Mermaid City raid happened and everyone was using fire abilities while being submerged under water?! The Mc even somehow managed to make an Aquarian tank catch fire?! Does the author not know that fire does burn under water??? How does any of that make sense.

Ms Song is a mermaid. Everyone else are villains. As a matter of fact, she should be in water because she'd die if out of water and everyone else SHOULD attack her because they are villains. What would she be expecting anyways?

mermaid yessir water boi let's go yandere yay

A surprisingly good isekai fish out of water story with good character development and world building. There are some iffy parts but read past them it's worth it.