Regarding that time I was Reincarnated as a Deep Sea Angler Fish... DSSF

The world as we knew it has sunken beneath a large body of ocean water, as sea creatures and aquatic monsters from the other side then comes on over through the portals, located around the world.

Earth has become entirely submerged in water, thereby making it the perfect habitat for oceanic life and sea creatures to prosper.

How will our main protagonist Arthur survive by being reincarnated as a deep-sea Angler Fish?
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Author's Notes/Additional Information:
This story will be a part of the《Sea Devil Incarnate》series that I am currently writing.

Released Schedule: Undecided
Chapter Length: 2500 - 3000
Point of View: First Person Perspective
I will eventually be posting this novel on Royalroad under the username of Luna24R.