Fish that have a tail shaped more like a crescent moon, like the Tuna, swim much faster because the shape of their tail reduces the amount of drag produced as they swim through the water. This can be beneficial for the open ocean, where speed helps in hunting and escaping from predators. The most common type of tail is called "homocercal", which means it is symmetrical in the upper and lower lobes of the tail. This applies to crescent shaped fins, but also more rounded fins, like an Angelfish or Clownfish. The rounded fin doesn't supply fish with speed but maneuverability. This means the fish has better control over quick, sharp movements, which is beneficial in environments like coral reefs where danger comes more suddenly. Fish that have a tail shaped more like a crescent moon, like the Tuna, swim much faster because the shape of their tail reduces the amount of drag produced as they swim through the water. This can be beneficial for the open ocean, where speed helps in hunting and escaping from predators. The most common type of tail is called "homocercal", which means it is symmetrical in the upper and lower lobes of the tail. This applies to crescent shaped fins, but also more rounded fins, like an Angelfish or Clownfish. The rounded fin doesn't supply fish with speed but maneuverability. This means the fish has better control over quick, sharp movements, which is beneficial in environments like coral reefs where danger comes more suddenly.