a jellyfish is not a single animal - it's actually a colony, and is an example of the evolution of multi-organ animals. also, it has no brain, heart, or bones and - because it's 98% water - evaporates on a beach.

a group of jellyfish is called a 'smack'.

the longest jellyfish ever recorded was half a football field long - 160 feet.

think doctor who is cool because he can regenerate? a small jellyfish (turritopsis dohrnii) has him beat; it's biologically immortal. in times of stress or attack, or if it is sick or old, it transdifferentiates its cells from free-swimming adult to polyp stage, essentially aging backwards. it can theoretically do this forever.