Fish school together in giant balls as a form of protection against predators. This behavior is known as shoaling, where fish swim closely together in synchronized movements. The main purpose of this behavior is to confuse and overwhelm predators, making it difficult for them to target a single fish. By swimming in a large group, fish increase their chances of survival as it creates a visual illusion for predators and reduces the likelihood of being caught. Additionally, fish in schools also benefit from increased efficiency in finding food and navigating their environment.

Overall, the formation of these giant balls of fish serves as a strategic defense mechanism that allows them to thrive and survive in their aquatic habitats.