These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Goddamned Bats: The swarm of jellyfish in stage 5, and the piranhas in stage 4 to a lesser extent.
Memetic Badass: The diver who has somehow managed to live in Midgardsorm's stomach for ten days. Even ignoring the fact that he'd run out of air within hours and has no source of drinkable water, there's also the parasitic trilobites that nearly flay you alive the moment you regain control and he has NO WEAPON to fend them off with except an ineffective sword (And even if that worked he has to sleep some time). His rather optimistic attitude and tone despite his situation, plus the fact that he looted the swallowed ships for treasure, a sword, and a GOLD CROWN HE WEARS ON HIS HELMET, also help.
Nightmare Fuel: The vast majority of the sea monsters, and some of the mini bosses, particularly if you have a fear of the ocean.
Squick: At the beginning of the North Sea, you find the corpse of a baby whale before lampreys suddenly shoot out of it to attack you.. Ugh.
That One Boss: Karkinos. Many expert players fell under his mighty pincers.
Scylla, the giant squid miniboss, will eventually begin ramming the player and is nearly impossible to deflect the attack of.