Rather than seaspeak with seal accent, I found that the shark's appearance was much more deus ex machina. With how close the sea was with a cliff, I would think shark stay away from such area. Maybe if a whale or dolphin showed up it would make a little bit more sense. Or small fishes. Then again, I have no idea how shark actually lives and their general living area.
But this point doesn't suprass the line for my suspension of disbelief because the shark was really amusing. I guess that's the whole deal actually with Beastars. Legosi can be animal Jesus as
@MilkDrinker above said, but honestly, that wouldn't be a surprise, feel like that's what the author intended to anyway.
So in conclusion, this story is just that good (at least, for me).