Are jellyfish considered sentient?

There are sensory nervous functions too, namely photosensitivity and gravity sensitivity. Jellyfish can react to stimuli, but this is not indicative of sentience: single celled organisms can do this too.

Are jellyfish self aware?

Many jellyfish have circadian or daily rhythms, which mean they behave differently during day and night. “Fly one to Tokyo and it would get jet lag just like we do,” Helm says. With this seemingly primitive nervous system, one part of a jellyfish body can be aware of, and respond to, the needs of another part.