How to Tell the Difference Between Shark & Dolphin Fins

Written by jess kroll
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How to Tell the Difference Between Shark & Dolphin Fins
Dolphin dorsal fins are smooth and rounded while a shark's is straight and angular. (Jupiterimages/ Images)

Although similar in appearance there are enormous difference between sharks and dolphin, the least of which being people generally enjoy swimming in the open water with dolphins but not with sharks. If a shark or dolphin is swimming close to the surface, often the only noticeable part of either is the dorsal fin cutting through the water. When this is the only sign whether the animal is a dolphin or a shark, it's important to tell quickly which one may be approaching before deciding whether to leave the water or not.

Skill level:
Moderately Easy


  1. 1

    Notice the shape of the fin, which is the quickest way of determining between a dolphin and shark fin. Dolphins have a smooth curve to the front of the fin and a similarly smooth curve at the back. Sharks have a straight and sharp dorsal fin that may cut backward or straight down at the end, with only very few having a slight rear curve.

  2. 2

    Count the number of fins. Sharks have a second, smaller fin between the dorsal and the tail. This smaller fin mirrors the shape of the dorsal fin and is only visible when swimming very close to the surface.

  3. 3

    Notice the texture of the fin. Although possibly damaged by boats or other previous encounters, dolphin dorsal fins are smooth in texture and streamlined. Sharks have a notched or ragged appearance at the rear of their fins. For some species of shark this may only be noticeable when very close.

  4. 4

    Notice how the fin is attached. While only visible when the animal is very close to the surface, a dolphin's fin ends at the rear in a smooth transition to the animal's back while a shark's fin has a gap between the rear edge of the fin and the back creating a detached tip.

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