There are more things to do than finishing the whole game the way it was intended, not every biome has a monster that can kill you.
You can swim with the pengwings, play with the sea monkeys, build a giant base in the starting area while playing in creative mode…, there might even be mods that completely disable the need to surface for air or make every creature passive so you can swim mwext to them in peace.
Yeah, you’re right. I had kind of forgotten about that part lol.
Even if you manage not to die in any of the horrific ways it’s still pretty violent.