Why does the old man in the book The Old Man and the Sea hate jelly fish?

The old man hates jellyfish because the creature's physical beauty is a deceptive facade.
In the story, the old man calls a Portuguese man-of-war jellyfish an "agua mala" and a "whore." The words "agua mala" directly translate to "bad water."
The term refers to the Portuguese man-of-war jellyfish, which is deceptively beautiful in all its iridescent brilliance. In reality, the jellyfish's long tentacles can deliver painful stings to its victims. It is said that the venom from the tentacles is more powerful than that of the most venomous snakes in the world.
After being stung, the victim's skin breaks out in extremely painful red welts. The sensation of pain is almost unbearable. This is why the old man hates jellyfish. Their beauty is deceptive, and it wreaks incapacitating pain on anyone unfortunate enough to cross their path.
In the story, there are small fish that are immune to the jellyfish's poison. However, no human being is immune. The narrator relates that the narrator, himself, has suffered painful welts on his arms and hands after coming in contact with the jellyfish's "filaments" on fishing lines.
Because of his hatred of the jellyfish, the old man is happy when he sees turtles eating them. He also receives great joy in stomping on the beached jellyfish after a storm.