The collective noun for a group of fish is a "school." However, it can also be referred to as a "shoal," which generally indicates a group of fish that are swimming together in the same direction, often for social or safety reasons. Fish form schools to find food more efficiently, evade predators, and conserve energy during swimming. The term can apply to various species of fish, and it reflects the social behavior and reliance on cooperation that many species exhibit in their natural habitats.