Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Underwater Animals Pack 2 Free.
Underwater Animals Pack 2 v1.1
Underwater Animals Pack 2 includes few fish species and underwater props:
-three types of corals and underwater plant
-koi carp, mandarin fish, powder blue tang, siganus guttatus, siganus javus, siganus and yellow tang fish.
All animated with four animations:
slow swim, swim,fast swim and bite.
Video preview avalible on forum topic of pack.