So in my world of Horizon, there is a sentient species known as the Jar'keth that lives in the inner ocean of Enceladus. They resemble a mix between eels and catfish, and are slightly smarter than humans.

Despite being smarter than humans, they live in a primitive state due to not having any hands, tentacles, or any other grabbing appendage. This is because they have stayed largely the same for the past 5 million years, because they simply did not have any reason to evolve. This is due in large part because Jar'keth are the apex predators of Enceladus.

Unlike on Earth, the food chain of the Inner Sea is chemosynthesis based, similar to the bottom of our oceans. Creatures resembling fully aquatic manatees graze on rocky fields of tubeworms. This is logically because there's no sunlight.

Most creatures there see through a mix of echolocation and heat vision similar to a snakes', but many also have bioluminescence, to help light their paths as well as lure in prey. The Jar'keth have only primitive eyes, but communicate through a language of bioluminescent flashes similar to morse code. They also use their flashes to lure in prey.

I want to know how plausible this is. While simple life could exist on Enceladus, I have no idea if complex life could.