Jellyfish
From Tardis Wiki, the free Doctor Who reference
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 resembled jellyfish in appearance. (BFBS: Something Changed)