Jellyfish

Jellyfish were a type of marine-dwelling organism native to Earth. There were also jellyfish-like creatures spread far and wide across the Universe.

Jellyfish were possibly related to Medusoid (DW: Frontier in Space) and Brakari (WC: Snowfall)

The Owse were outer-space jellyfish native to planet Kaesov that were sensitive to shifts in reality. The Doctor kept one on board his TARDIS for a time. (PDA: The Quantum Archangel)

The Yesodi (species), who released toxic radiation, resembled Jellyfish in appearance. (BFBS: Something Changed)