From the Super Mario Wiki, the Mario encyclopedia

Finleys are a group fish enemies in Donkey Kong Country: Tropical Freeze. The Blue and Red Finleys look and behave almost identically, continuously swimming on set paths, though apart from color, Red Finleys swim faster than Blue Finleys. Green Finleys are entirely different from the other two variations, as they have a different appearance, are never faced in water and have different behaviors. All Finleys can be defeated with basic attacks.