Thank you for appreciating my game !
The element of surprise with the fishes is what I was aiming for so I am glad it worked (I wanted to subvert expectations, as when a huge mass is mentioned people may think there is some sort of leviathan or megalodon but it was the fish all along. Also that explains why the intro says that the mass "vanished" as when the swarm disperses it is no longer detected by the radar).
Sound is definitely something lacking right now that I want to add.
There also is some more interesting content that could be added, maybe exploiting a bit more the diving mechanic.