Download Tail Animator Free Unity. 

⚡ Tail Animator is a package of behaviors simulating elastic tail movement with procedural animation giving many new capabilities to you!
This animator will add much more realism and smoothness to your
keyframed animations of tail to just animate it for you without the need of making animations in other software.

✍ You can add tail elasticity to anything you want:
capes / plants / tentacles / arms / whole body (it needs bones or separated models) Possibilities are limited only by your mind.
Package comes with tool to create skinned meshes with bones just inside unity.
(mainly for tail type models, it’s not creating full humanoid skeleton for example)

☄️ Component reacts with changes on object’s position / rotation / scale.
Just add component to object you want to animate elastic, define root transform
(or bone) and play with parameters.