This was my first attempt at using the Niagara particle system that is in Unreal Engine 4.
You can see the system in action within the concept mermaid game I was apart of.
This particle system has 2 aspects to it, the attractor which moves around a circle with random force, and the fish which within it the leader determines which attractor randomly to swim towards. This is done with login within the scratch pad and point attraction force.
It's still a bit rusty but adds to the underwater environment greatly and is reusable for other fish particle systems ;)
The sad soy sauce fish was modeled and unwrapped in 3ds Max and textured in Substance 3D Painter.
Video moving around the still image of the flock
Preview of the particle system in unreal's editor
The particle system in the game
A smaller fish flock that was done with the same logic just less fish.