My intelligent alien species looks like a Koosh Ball:
They use biological "Flashlights" based on bioluminescence which uses sulfur as an oxidizing agent instead of oxygen.
This species lives on a hypothetical moon of Epsilon Eridani b which has a subsurface ocean. They live 50km deep in this ocean, where the pressure is about 0.5 GPa. This happens to also be at the seafloor of such an ocean.
They have 4 different types of tendrils. About half of them are "feelers" which are mainly used for four senses: "hearing" which is really just feeling vibrations, a sense of smell caused by the olfactory sensors which cover the tendrils, magnetoreception caused by a small amount of magnetized iron in some of the feelers which pulls them ever so slightly to the north, and finally a sense of touch which is quite literally just nerves running down the length of all of the tendrils.
Two types of tendrils are dedicated to catching prey: the "sticky" tendrils, which have a slight static charge, pulling in small particles such as bits of algae, and the "twisty" tendrils which are designed to trap larger prey by wrapping around them, and preventing them from intaking vital resources.
The final type of tendril is the "flashlight" tendrils, which have fiber-optic properties and a bioluminescent bulb at their base, which illuminates whatever the tendril is pointed at.
The species also have rudimentary light sensors on the "flashlight" tendrils. At the base of the tendril where the bioluminescent bulb is, there is also a rudimentary eyeball which uses similar mechanisms to that of Earth eyeballs, but with a much lower resolution than a human's, and that don't have any cone cells for detecting color. They only have rod cells which detect brightness.
This is mostly based on real-life evolution and science, along with answers to a few other questions on SE, with only a few deviations that I think are quite plausible.
What do you think? Is my idea plausible given real world science and biology? Don't hesitate to point out flaws just because it's well-developed. I want honest answers.