Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Fish School Goldfish Free.
Fish School Goldfish v1.32
Fish School is perfect for underwater scenes. This asset is very simple to use , simply drag the prefab to the stage. Commented inspector editor will assist in achieving the desired result.
Demo Page | Video
• Drag & Drop Fish School
• Gizmos that shows roaming area
• Simple UV map, easy to change texture
• Easily customize amount, size and speed
• 292 tris animated model
• 1024x1024px texture/normal resolution
• Easy custom models
• Includes Bubbles and Demo Scene
• Obstacle Avoidance
• Distance Disable Script
• C# Scripts
• Custom Rim Lit Shaders
Compatible with Unity 5.1 up to new versions of Unity(2019+)
Support available for assistance if any problems should occur.