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How to Know If You're Seeing a Dolphin or a Shark

While dolphins and sharks are certainly different animals, they have several anatomical similarities that make them difficult to distinguish in the water. They both have triangular dorsal fins that appear when they swim close to shore, and they both have gray, torpedo-shaped bodies. They also have side fins that protrude noticeably from their bodies. If you swim or sail in the ocean, it is important to distinguish between these two animals.

Instructions

- 1
  Look at the shape of the dorsal fin, which is the fin on the animal's back. Sharks have a triangular shape to their dorsal fin, while the dorsal fin of a dolphin is curved back at the tip.
- 2
  Watch how the animal moves its tail. Dolphins move their tails up and down to propel themselves through the water while sharks move their tails from side to side.
- 3
  Look at the tail's orientation. Dolphin tails are oriented horizontally while shark tails are vertical.
- 4
  Count the dorsal fins. Some sharks have a second dorsal fin on their back that is situated closer to their tail. If you see more than one dorsal fin, it is definitely a shark.
- 5
  Look to the side of the animal's head. Sharks are fish and have slash-like gills along the sides of their heads, while dolphins are mammals and have lungs.

Animals & Science