Better than the flocking algorithm, the schooling algorithm, works underwater.

's' to save
'a' to start/stop the animation.

You can create up to five different groups of fishes. You can set some of them to zero if you want less. For each group, you can set the base color of the fishes, which will still have some slight variations.

There are two colors for plants that will be shared between them, so you need at least two plants if you want to see both.