If you spot a gray dorsal fin sticking out of the ocean along Georgia’s coast, the fin probably belongs to a dolphin or a shark.

But which one?

Usually a dolphin’s dorsal fin has a curved tip while a shark’s is more triangular-shaped. Most dolphins have only one fin on their backs, but some sharks have a second smaller dorsal fin close to the tail.

Also, dolphins move their horizontal tails up and down; sharks move their vertical tails side to side. These differences are good to know, especially if you’re swimming in the ocean rather than observing from a boat!