Jellyfish were a type of marine-dwelling organism native to Earth. There were also jellyfish-like creatures spread far and wide across the universe.
When Fu Peng invited the Third Doctor to dinner, he told him they were having dried squid and stewed jellyfish. (TV: The Mind of Evil)
Thawn called Kroll an "overgrown jellyfish". (TV: The Power of Kroll)
Giant creatures which looked like jellyfish lived on Jobis. (AUDIO: The Rocket Men)