Sam confirmed his suspicions.
There was indeed a type of beast in this area.
Only one beast. But rather than calling it a beast, it is more suitable to call it a plant species.
This is called Blue mucus algae.
Even though it is called algae, unlike other algae it doesn't require sunlight, in fact, it is quite repulsive to it.
This type of algae is somewhat peculiar. The blue-colored mucus it excretes gives on an illusion that it is perfectly clear water.
But one couldn't be more wrong. It latches on the rocks underwater and there will be some tendrils that will be formed over its surface.
These tendrils envelope whatever prey that comes towards them and will suck the flesh away. That's right, they will suck the flesh bit by bit. There would be only bones left no matter the beast.
They are quite repulsive to light and heat. They can even deal with some beasts stronger than them if they are high in numbers.