Here's why:
* Powerful Propulsion: The caudal fin is the largest and most powerful fin on a fish's body. It provides the main force for forward movement and turning.
* Lateral Movement: The caudal fin's shape allows it to move side-to-side. By swishing its tail to one side or the other, the fish can generate a force that pushes it in the opposite direction, creating a turn.
While other fins (like the pectoral and pelvic fins) can help with stability and maneuvering, the caudal fin is the primary force behind directional changes.